Position weight matrices (PWMs) have become a tool of choice for the identification of transcription factor binding sites in DNA sequences. PWMs are compiled from experimentally verified and aligned binding sequences. PWMs are then used to computationally discover novel putative binding sites for a given protein. DNA-binding proteins often show degeneracy in their binding requirement, the overall binding specificity of many proteins is unknown and remains an active area of research. Although PWMs are more reliable predictors than consensus string matching, they generally result in a high number of false positive hits. A previous study introduced a novel method to PWM training based on the known motifs to sample additional putative binding sites from a proximal promoter area. The core idea was further developed, implemented and tested in this thesis with a large scale application. Improved mono- and dinucleotide PWMs were computed for Drosophila melanogaster. The Matthews correlation coefficient was used as an optimization criterion in the PWM refinement algorithm. New PWMs keep an account of non-uniform background nucleotide distributions on the promoters and consider a larger number of new binding sites during the refinement steps. The optimization included the PWM motif length, the position on the promoter, the threshold value and the binding site location. The obtained predictions were compared for mono- and dinucleotide PWM versions with initial matrices and with conventional tools. The optimized PWMs predicted new binding sites with better accuracy than conventional PWMs.

<p>Co-axial dripping is one of the many ways to make drops with a core-shell structure for encapsulated materials. However, in systems where the capsule components are not density matched or surfactants are not used, the shell will eventually thin and break if not solidified in time. If the shell fails before solidifying, the core will leak out and result in a non-functional capsule. This study assumes that all capsules will fail once the core has reached 80% eccentricity, meaning a shell region has thinned to 20% of its original thickness (~70 µm). In reality, rupture of the shell depends more on stochastic defects and disturbances, but locally decreasing the shell thickness will increase the probability of capsule rupture. With this assumption, the survival time of a core-shell drop is inversely proportional to the relative velocity of the inner drop, where the greater this relative velocity, the faster the shell phase will thin. Stoke's law is generally used to approximate the speed of a sphere in a fluid. However, this study demonstrates that Stoke's law is insufficient for predicting the inner drop's motion for a compound drop. This is due to internal flows that develop within all fluid drops because of shear forces on the drop’s external face during freefall. For core-shell drops, prior studies report how the inner drop velocity can change in magnitude and direction as a function of its eccentricity, meaning its position within the outer drop. Since previous studies did not analyze this core-shell drop relationship with a 50 vol% core and a high viscosity shell, a model was built in COMSOL Multiphysics to understand how the claims from literature would apply to a previous encapsulation study (Betancourt, 2021). The model was also put through a series of validation tests that confirmed the model’s ability to accurately represent the speed and direction of inner drop motion. The final model configuration was then used to identify the transition point between buoyancy-driven and internal flow-driven failure modes observed during the production of core-shell drops in a previous encapsulation study for phase change materials (Betancourt, 2021). The model results showed how the estimated inner drop velocity was significantly reduced once accounting for the internal flows within the shell phase of a compound drop. While this study does help characterize the motion of an inner drop and could be used to find a material system with a favorable velocity profile, it is still recommended to use an in-air curing system to produce concentric capsules. Achieving a concentric capsule would still require this co-axial dripping setup to be modified significantly. </p> <p>Betancourt-Jimenez, D., Wells, B., Youngblood, J. P., & Martinez, C. J. (2021). Encapsulation of biobased fatty acid amides for phase change material applications. <em>Journal of Renewable and Sustainable Energy</em>, <em>13</em>(6), 064101. https://doi.org/10.1063/5.0072105</p>

<p>The subcutaneous injection has emerged as a common approach for self-administration of biotherapeutics due to the patient comfort and cost-effectiveness. However, the available knowledge about transport and absorption of these agents after subcutaneous injection is limited. Here we aim to find drug distribution in the tissue and lymphatic uptake after subcutaneous (SC) injection. In the first part of the study, a mathematical framework to study the subcutaneous drug delivery from injection to lymphatic uptake is presented. A three-dimensional poroelastic model is exploited to find the biomechanical response of the tissue by taking into account tissue deformation during the injection. The results show that including tissue deformability noticeably changes tissue poromechanical response due to the significant dependence of interstitial pressure on tissue deformation. Moreover, the importance of the amount of lymph fluid at the injection site and injection rate on the drug uptake to lymphatic capillaries is highlighted. Finally, the variability of lymphatic uptake due to uncertainty in parameters, including tissue poromechanical and lymphatic absorption parameters, is evaluated. It is found that interstitial pressure due to injection is the major contributing factor in short-term lymphatic absorption, while the amount of lymph fluid at the site of injection determines the long-term absorption of the drug. Finally, it is shown that the lymphatic uptake results are consistent with experimental data available in the literature.</p><p>In the second part, drug transport and distribution in different tissue layers are studied. A single-layer model of the tissue as a base study was first explored. During injection, the difference between the permeability of the solvent and solute results in a higher drug concentration proportional to the inverse of the permeability ratio. Then the effects of layered tissue properties with primary layers, including epidermis, dermis, subcutaneous, and muscle layers, on tissue biomechanical response to injection and drug transport are studied. The drug distributes mainly in the SQ layer due to its lower elastic moduli. Finally, the effect of secondary tissue elements like the deep fascia layer and the network of septa fibers inside the SQ tissue is investigated. The Voronoi algorithm is exploited to create random geometry of the septa network. It is shown how drug molecules accumulate around these tissue components as observed in experimental SC injection. Next, the effect of injection rate on drug concentration is studied. Higher injection rates slightly increase the drug concentration around septa fibers. Finally, it is demonstrated that the concentration-dependent viscosity increases the concentration of biotherapeutics in the direction of septa fibers.</p><p>In the third part of this thesis, a poro-hyperelastic model of the tissue is exploited to find the biomechanical response of the tissue together with a transport model based on an advection-diffusion equation in large-deformation poro-hyperelastic Media. The process of mAbs transport to the lymphatic system is explored. This process has two major parts. First, the initial phase, where mAbs are dispersed in the tissue as a result of momentum exerted by injection. This stage last for only a few minutes after the injection. Then there is the second stage, which can take tens of hours, and as a result, monoclonal antibodies (mAbs) molecules are transported from the subcutaneous layer towards initial lymphatics in the dermis to enter the lymphatic system. In third chapter, both stages are studied. The process of plume formation, interstitial pressure, and velocity development is explored. Then the effect of the injection device, injection site, and sensitivity of long-term lymphatic uptake due to variability in permeability, diffusivity, viscosity, and binding of mAbs are investigated. Then the results are used to find an equivalent lymphatic uptake coefficient that is widely used in pharmacokinetic (PK) models to study the absorption of mAbs. We show that the injection rate is the least, and the injection site is the most important parameter in the uptake of mAbs. Injection depth and mAbs dose also significantly alter lymphatic absorption. Finally, the computational model is validated against experimental studies available in the literature.</p>

<p>  </p> <p>In gas turbines, the hot gas exiting the combustor can be as high as 2000 ^oC, and some of this hot gas enter into the space between the stator and rotor disks (wheelspace). Since the hot gas entering with its high temperatures could damage the disks, hot-gas ingestion must be minimized. This is done by using rim seals and by introducing a flow of cooler air from the compressor (sealing flow) into the wheelspace. </p> <p>Ingress and egress into rim seals are driven by the stator vanes, the rotor and its rotation, and the rotor blades. This study focuses on the first-stage turbine, where ingress could cause the most damage and has two parts. The first part focuses on understanding ingress and egress driven by the rotor and its rotation, known as rotationally-induced ingress, by studying ingress about an axial seal in a stator-rotor configuration without vanes and without blades. The second part focuses on understanding ingress and egress driven by stator vanes, known as externally-induced ingress, by studying a stator-rotor configuration with vanes but no blades, where the ratio of the external Reynolds number to the rotational Reynolds number is 0.538. For both parts, solutions were generated by wall-resolved large-eddy simulation (LES) based on the WALE subgrid model and by Reynolds-averaged Navier-Stokes (RANS) based on the SST model. For both stator-rotor configurations, the grid-independent solutions obtained were compared with available experimental data.   </p> <p>Results obtained for the configuration without vanes and blades show Kelvin-Helmholtz instability (KHI) to form even without swirl from the hot-gas flow and to create a wavy shear layer on the rotor. Also, Vortex shedding (VS) occurs on the backward-facing side of the seal and impinges on the rotor side of the seal. The KHI and VS produce alternating regions of high and low pressures about the rotor-side of the axial seal, which cause ingress to start on the rotor side of the seal. Results obtained for the configuration with vanes but no blades show both LES and RANS to correctly predict the coefficient of pressure, C_p, upstream of the axial seal. However, only LES was able to correctly predict the sealing effectiveness. This shows C_p by itself maybe is inadequate in quantifying externally-induced ingress. One reason why RANS was unable to predict sealing effectiveness is significantly under predicting the pressure drop on the rotor surface, which affected the pressure variation along the hot-gas path and hence the pressure difference across the axial seal, which ultimately drives ingress. </p>

<p>  </p> <p>Heat pipes and vapor chambers are passive two-phase heat transport devices that are used for thermal management in electronics. The passive operation of a heat pipe is facilitated by capillary wicking of the working fluid through a porous wick, and thus is subject to an operational limit in terms of the maximum pressure head that the wick can provide. This operational limit, often termed as the capillary limit, is the maximum heat input at which the pressure drop in the wick is balanced by the maximum capillary pressure head; operating a heat pipe or a vapor chamber above the capillary limit at steady-state leads to dryout. It thus becomes important to predict the performance of heat pipes and vapor chambers and explore the parametric design space to provide guidelines for minimized thermal resistance while satisfying this capillary limit. An increasingly critical aspect is to predict the transient thermal response of vapor chambers. Moreover, heat pipes and vapor chambers are extensively being used in electronic systems where the power input is dictated by the end-user activity and is expected to even exceed the capillary limit for brief time intervals. Thus, it is imperative to understand the behavior of heat pipes and vapor chambers when operated at steady and transient heat loads above the capillary limit as dryout occurs. However, review of the literature on heat pipe performance characterization reveals that the regime of dryout operation has been virtually unexplored, and thus this thesis aims to fill this critical gap in understanding.</p> <p>The design for minimized thermal resistance of a vapor chamber or a heat pipe is guided by the relative contribution of thermal resistance due to conduction across the evaporator wick and the saturation temperature gradient in the vapor core. In the limit of very thin form factors, the contribution from the vapor core thermal resistance dominates the overall thermal resistance of the vapor chamber; recent work has focused on working fluid selection to minimize overall thermal resistance in this limit. However, the wick thermal resistance becomes increasingly significant as its thickness increases to support higher heat inputs while avoiding the capillary limit. A thermal resistance network model is thus utilized to investigate the importance of simultaneously considering the contributions of the wick and vapor core thermal resistances. A generalized approach is proposed for vapor chamber design which allows <em>simultaneous</em> selection of the working fluid and wick that provides minimum overall thermal resistance for a given geometry and operating condition. While the thermal resistance network model provides a convenient method for exploring the design space, it cannot be used to predict 3-D temperature fields in the vapor chamber. Moreover, such thermal resistance network models cannot predict transient performance and temperature evolution for a vapor chamber. Therefore, an easy-to-use approach is proposed for mapping of vapor chamber transport to the heat diffusion equation using a set of appropriately defined effective anisotropic thermophysical properties, thus allowing simulation of vapor chamber as a sold conduction block. This effective anisotropic properties approach is validated against a time-stepping analytical model and is shown to have good match for both spatial and transient temperature predictions.</p> <p>Moving the focus from steady-state and transient operation of vapor chambers, a comprehensive characterization of heat pipe operation above capillary limit is performed. Different user needs and device workloads can lead to highly transient heat loads which could exceed the notional capillary limit for brief time intervals. Experiments are performed to characterize the transient thermal response of a heat pipe subjected to heat input pulses of varying duration that exceed the capillary limit. Transient dryout events due to a wick pressure drop exceeding the maximum available capillary pressure can be detected from an analysis of the measured temperature signatures. It is discovered that under such transient heating conditions, a heat pipe can sustain heat loads higher than the steady-state capillary limit for brief periods of time without experiencing dryout. If the heating pulse is sufficiently long as to induce transient dryout, the heat pipe may experience an elevated steady-state temperature even after the heat load is reduced back to a level lower than the capillary limit. The steady-state heat load must then be reduced to a level much below the capillary limit to fully recover the original thermal resistance of the heat pipe. The recovery process of heat pipes is further investigated, and a mechanism is proposed for the thermal hysteresis observed in heat pipe performance after dryout. A model for <em>steady-state</em> heat pipe transport is developed based on the proposed mechanism to predict the parametric trends of thermal resistance following recovery from dryout-induced thermal hysteresis, and the model is mechanistically validated against experiments. The experimental characterization of the recovery process demonstrates the existence of a maximum hysteresis curve, which serves as the worst-case scenario for thermal hysteresis in heat pipe after dryout. Based on the learnings from the experimental characterization, a new procedure is introduced to experimentally characterize the steady-state dryout performance of a heat pipe.</p> <p>To recover the heat pipe performance under steady-state, it has been shown that the heat input needs to be lowered down or <em>throttled</em> significantly below the capillary limit. However, due to the highly transient nature of power dissipation from electronic devices, it becomes imperative to characterize heat pipe recovery from dryout under transient operations. Hence, power-throttling assisted recovery of heat pipe from dryout has been characterized under transient conditions. A minimum throttling time interval, defined as time-to-rewet, is identified to eliminate dryout induced thermal hysteresis using power throttling. Dependence of time-to-rewet on throttling power is explored, and guidelines are presented to advise the throttling need and choice of throttling power under transient conditions. </p> <p>The experimental characterization of heat pipe operation at pulse loads above the capillary limit and power throttling following the pulse load helped define the dryout and recovery performance of a heat pipe. Next, a physics-based model is developed to predict the heat pipe <em>transient</em> thermal response under dryout-inducing pulse load and power throttling assisted recovery. This novel model considers wick as a partially saturated media with spatially and temporally varying liquid saturation, and accounts for the effect of wick partial saturation in heat pipe transport. The model prediction are validated against experiments with commercial heat pipe samples, and it is shown that the model can accurately predict dryout and recovery characteristics, namely time-to-dryout, time-to-rewet, and dryout-induced thermal hysteresis, for heat pipes with a range of wick types, heat pipe lengths and pulse loads above the capillary limit. </p> <p>The work discussed in this thesis opens certain questions that are expected to guide further research in this area. First, the thermal hysteresis mechanism proposed could be further validated with direct visualization of the liquid in a vapor chamber. To achieve this, X-ray microscopy is proposed as a viable option for the imaging <em>in situ</em> wetting dynamics in a vapor chamber. Second, the model developed to predict the dryout and recovery characteristics of the heat pipe can be used to design heat pipe with improved performance under pulse loads and power throttling. Third, novel wick designs can be explored that utilize the understanding developed of governing mechanisms for recovery from dryout, and can eliminate thermal hysteresis at powers closer to capillary limit. Fourth, the modeling approach can be extended to predict dryout and recovery trends in vapor chamber since the heat transfer pathways in a vapor chamber are different than those of a heat pipe. Fifth, and lastly it was observed several times during experiments that some of the heat pipe samples would exhibit complete dryout (sudden catastrophic rise in temperature and thermal resistance at the point of dryout) whereas other samples would exhibit partial dryout (noticeable but small increase in thermal resistance at dryout) at operating powers just above the capillary limit. Exploring and explaining the cause of complete dryout, in particular, would be an extremely valuable contribution to the heat pipe research. </p> <p>The work discussed in this thesis has led to the comprehensive development of a functional and mechanistic understanding of heat pipe operation above the notional capillary limit. The experimental procedures developed in this work are utilized to characterize a heat pipe performance under dryout and recovery. The models based on the mechanistic understanding developed from experimental characterization of dryout and recovery operation of a heat pipe have been experimentally validated and are useful for predicting heat pipe performance under dryout-inducing pulse loads and power-throttling.   </p>

<p>  </p> <p>With economies shifting towards net-zero carbon emissions, there is an increased interest in carbon-free energy carriers. Hydrogen is a potential carbon-free energy source. However, it poses several production, infrastructural, and safety challenges. Ammonia blends have been identified as a potential hydrogen carrier and fuel for gas turbine combustion. Partially cracked ammonia mixtures consist of large quantities of hydrogen that help overcome the disadvantages of pure ammonia combustion. The presence of nitrogen in the fuel blends leads to increased NO_x emissions, and therefore lean premixed combustion is necessary to curb these emissions. Understanding the flame features, precursors, and dynamics of blowout of such blends due to lean conditions is essential for stable operation, lean blowout prediction, and control. </p> <p><br></p> <p>In this study, high-fidelity large eddy simulations for turbulent premixed ammonia/hydrogen/nitrogen-air flames in an axisymmetric, unconfined, bluff-body stabilized burner are performed to gain insights into lean blowout dynamics. Partially cracked ammonia (40% NH₃, 45% H₂, and 15% N₂, by volume) is chosen as fuel since its laminar burning velocity is comparable to CH4-air mixtures. A finite rate chemistry model with a detailed chemical kinetic mechanism (36 species and 247 reactions) is utilized to capture characteristics of various species during blowout. A comprehensive study of the flow field and flame structure for a weakly stable burning at an equivalence ratio of 0.5 near the blowout limit is presented. Further, the effects of blowout on the heat release rate, vorticity, distribution of major species, and ignition radicals are studied at four time instances at blowout velocity of 70 m/s. Since limited data is available on turbulent premixed combustion of partially cracked ammonia, such studies are essential in understanding flame behavior and uncertainties with regard to blowout.</p>

<p dir="ltr">Addressing the pressing need for reduced carbon emissions, Turbulent Jet Ignition (TJI) emerges as a promising technology for ultra-lean combustion, offering enhanced thermal efficiencies and minimized cyclic variability in spark-ignited engines. To facilitate rapid testing and integration of this technology, a robust computational modeling framework is crucial. This study delves into the predictive capabilities of computational models for main-chamber ignition and premixed flame propagation using a single-cycle TJI rig measured by Biswas et al. (Applied Thermal Engineering, volume 106, 2016). Employing an open-source compressible flow simulation solver with Large Eddy Simulation (LES) for turbulence modeling, the investigation integrates the conventional Laminar Finite Rate Chemistry (LFRC) model alongside the transported Probability Density Method (PDF) for turbulence-chemistry interaction. A fully-consistent Eulerian Monte-Carlo Fields (EMCF) method is utilized to approximate the transported PDF, while Interaction by Exchange with Mean is employed to close micro-mixing terms in stochastic differential equations. A reduced chemical reaction mechanism with 21 species and 84 reactions (DRM-19) is used for solving chemical kinetics, and a double Gaussian energy deposition model is used to approximate the spark ignition in the pre-chamber. An unstructured O-grid mesh with 0.3 million cells in the pre-chamber and 1 million cells in the main chamber is employed. Results are divided into two phases: pre-chamber initialization and full TJI simulations. Validation of the predicted pre-chamber flame propagation and the lean ignition in the main-chamber is carried out by using available experimental data. Under quiescent conditions, both the LFRC and transported PDF methods largely underestimate the flame speed and subsequent pressure growth in the pre-chamber. A linear momentum forcing technique is applied to investigate the impact of initial turbulence in the pre-chamber, demonstrating a notable influence on flame propagation. Fine-tuning of the forcing coefficient reproduces the sudden pressure growth observed in the experiment. The experimentally validated pre-chamber simulation serves as the initial condition for the full TJI simulations. It is found that the LFRC model fails to predict lean-ignition in the main-chamber, resulting in a misfiring event. Incorporation of turbulence-chemistry interaction using the transported PDF method substantially improves the prediction of the ignition event in the main-chamber, achieving fair qualitative agreement and quantitative validation of combustion parameters within 10% of the reported experimental data. The rich simulation results consisting of a full set of statistical description of the thermo-chemical states enable us to gain deep insights into the ignition mechanisms in the main chamber, which is limited when done experimentally. A novel dual ignition phenomenon is revealed in the TJI rig for the first time. Initially, a primary ignition kernel is formed at a downstream location which eventually detaches from the main jet. As the jet momentum decreases, a secondary ignition event follows, this time at a more upstream location which eventually combines with the primary ignition kernel to form a single connected flame front. Investigation of these ignition sequences in chemical composition space reveal distinct differences between the two. The primary ignition event in the main-chamber is followed by a large concentration of active radicals from the pre-chamber jet, accelerating the chain-branching steps, characterizing what has been referred to as flame ignition. In contrast, the secondary ignition occurs in the absence of active radicals in the pre-chamber jet, hence characterized as jet ignition. Further analysis of the effect of pre-chamber jet characteristics on lean ignition in the main-chamber is conducted by setting up cases with different initial pressure ratios (p_r^o) between the two chambers, a non-dimensional parameter, ranging from 1.2 to 3.2. As the initial pressure ratio increases, jet momentum increases, with dual ignition observed in cases above p_r^o= 2.2. Case with p_r^o= 3.2 lead to misfiring. The effect of ignition sequence on global combustion characteristics of TJI is analyzed. Dual ignition events lead to non-monotonicity in combustion characteristics such as global reaction progress variable, flame penetration, and global heat release rate. In dual ignition events, although the rate of fuel consumption and global heat release rate is initially lower, the secondary ignition leads to a sudden increase in flame surface area, resulting in a sudden jump and promoting the overall performance of the TJI system.</p>

<p dir="ltr">Transportation and energy production industries strongly rely on improvements in gas turbine performance. The quantification of these improvements is dependent on the accuracy of the measurements performed during testing. An increase of 0.5\% in efficiency is sufficient to secure a new development program worth millions of dollars, but in the case of temperature measurements, uncertainties below 0.5 K are required, which presents a challenge. This work selects heat flux estimation and total temperature measurement uncertainties as major contributors for efficiency uncertainty.</p><ul><li>Heat flux measurements are critical to evaluate the impact on the efficiency. Additionally, thermal fatigue in turbine airfoils defines the life cycle of the engine core. This work performs an estimation of the heat transfer via a simplified numerical model that uses infrared (IR) measurements in the surface of the casing to predict the temperature of the passage wall. The model is validated with real cool-down data of the turbine to yield results within a 10\% of the actual temperature.</li><li>Total temperature measurement suffers from errors due to heat transfer effects in the probe. Two dominant sources of errors are convection and conduction between the thermocouple wires, the probe support, and the flow. These effects can be treated in two different categories: the velocity error, created by a non-isentropic reduction of the flow velocity upstream the thermocouple junction, and the thermal equilibrium effects between the junction and the probe support, involving heat transfer through the wire to the shield and the probe stem due to temperature differences between each component (the so-called \emph{conduction error}). An open jet stand is used to evaluate the effects of velocity error at various Mach numbers. The conduction error is addressed with the design and manufacturing of dual-wire thermocouple probes. The readings from two wires with different length-to-diameter ratios are used to correct for the flow total temperature. This probe yielded a recovery factor of 0.99 +/- 0.01 at Mach 0.6.</li></ul><p></p>

<p>  </p> <p>Cavitation is one of the most common causes of failures in axial piston machines. Due to the detrimental effects that cavitation has on unit performance, it is of important consideration both in the design of new units and in defining the operational limits of existing market products. The work in this thesis aimed to contribute to the current knowledge in both areas, with a focus on design considerations with respect to cavitation scalability, and on operating conditions by measuring cavitation severity under separate and combined inciting parameters. Though the application of unit scaling is common in industry for the design of pump families, there have been no comprehensive attempts to quantify whether cavitation in fluid power units may be adequately accounted for in published scaling laws. In this thesis, the scalability of cavitation phenomena was examined through a CFD scaling study performed using a modified version of the Full Cavitation Model.  Results indicate that linear scaling is consistent in maintaining volumetric efficiency performance within 1% across scaled units up to eight times larger or smaller than the baseline. However, the gas and vapor volume distributions vary significantly between scaled units, due largely to the linear non-scalability of fluid inertia and turbulent factors. Physical exchange between phases within a working fluid was shown to be time-dependent, such that the scaled-down unit exhibits bubble collapse rates up to 30% and 150% greater than the baseline and scaled-up units, respectfully. Considering these effects, the presented work demonstrates a potential for increased cavitation damage area when downscaling a unit and reduced risk in upscaling, despite the scaling law being a reliable indicator for volumetric efficiency. </p> <p>To define a more complete study of cavitation under a variety of operating conditions and inciting parameters, this a new experimental procedure and testing circuit was proposed with focus on repeatability by controlled pressure drops and preliminary quantification of inlet fluid quality. By measuring cavitation conditions under pressure starvation, incomplete filling, and combinations thereof, the direct effect of different inception methods on unit performance was shown to be readily identifiable. Through visualization of the inlet flow, reduction in inlet pressure levels was correlated to fluid cloudiness levels and bubble size, with transparency loss at 0.0 bar_g and transition from bubbly to plug flow at -0.4 bar_g. Incomplete filling-induced cavitation was also shown to be detectable by inlet flow conditions, with a distinct change in bubble coalescence rate when operating under shaft speeds greater than or equal to fill speed for a given inlet pressure. </p>

<p>Many industrial organizations invest heavily in modeling and simulation (M&S) to support the design process. The primary business motivation for M&S is as a cheaper and faster alternative for obtaining information towards a better understanding of system behavior or to help with decision making. However, M&S predictions are known to be inexact because models and simulations are mathematical approximations of reality. To ensure that models are applicable for their intended use, organizations must collect evidence that the M&S is credible. Verification, validation, and uncertainty quantification (VVUQ) are the established methods for collecting this evidence. Structured frameworks for building credibility in M&S through VVUQ methods exist in the scientific literature but these frameworks and methods are generally not well developed, nor well implemented in industrial environments. The core motivation of this work is to help make existing VVUQ frameworks more suitable for industry.</p> <p>As part of this objective, this work proposes a new credibility assessment that turns VVUQ results into an intuitive, numerical decision-making metric. This credibility assessment, called the Credibility Index, identifies the important aspects of credibility, extracts the relevant VVUQ results, and converts the results into an overall Credibility Index score (CRED). This CRED score is unique for each specific prediction scenario and serves as an easy-to-digest measure of credibility. The Credibility Index builds upon widely accepted definitions of credibility, well-established VVUQ frameworks, and decision theory.</p> <p>The Credibility Index has been applied to several prediction scenarios for two publicly available benchmark problems and one Rolls-Royce funded subsystem case; all examples relate to the aerodynamic design of turbine-engine compressors. The results from these studies show how the Credibility Index serves as a decision-making metric, supplements traditional M&S outputs, and guides VVUQ efforts. A product feedback study, involving model end-users in industry, compared the Credibility Index to three other established credibility assessments; the study provides evidence that CRED consistently captures all key aspects of information quality when informing end-users on the credibility of model predictions. Due to the industry partnership, this research already has multiple avenues of practical impact, including implementation of the structured VVUQ and credibility framework in an industrial toolkit and workflow. </p>