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Der mit flüssigem Natrium gefüllte Druckbehälter eines Präzessionsexperimentes unterliegt im Betrieb einer Vielzahl an Belastungen. Neben den aus der Rotation und Präzession resultierenden Fliehkräften und dem gyroskopischen Moment müssen ebenfalls die fertigungsbedingten Unwuchten sowie die Fluid-Struktur-Interaktion berücksichtigt werden. Darüber hinaus stellen die bei der Erwärmung bzw. Abkühlung auftretenden thermischen Spannungen eine wesentliche Beanspruchung dar. Es wird ein Algorithmus vorgestellt, der es ermöglicht, alle diese transienten und winkelabhängigen Lasten bei minimalem Rechenaufwand in den Berechnungsprozess einzubeziehen und die für den statischen und zyklischen Festigkeitsnachweis nach FKM-Richtlinie maßgeblichen Beanspruchungen zu identifizieren. Dies ermöglicht die vollflächige Berechnung des Auslastungsgrades in ANSYS Workbench.

In diesem Beitrag wird die Wirksamkeit statischer Mischer in verschiedenen Anordnungen und Strömungskonfigurationen untersucht. Auf Grundlage umfangreicher numerischer Untersuchungen werden die Anwendungsgrenzen von spiralförmigen statischen Mischern zur Verbesserung des Wärmeübergangs in Kühlkanälen von Werkzeugmaschinen aufgezeigt. Die numerischen Simulationen wurden mit der kommerziellen Computational-Fluid-Dynamics (CFD)-Software, ANSYS Fluent 2020 R2, durchgeführt. Diese Studie zeigt, dass es einen optimalen Anwendungsbereich für statische Mischer als Wärmeaustauschverstärker in Abhängigkeit von der Strömungsgeschwindigkeit, dem übertragenen Wärmestrom und der Wärmeleitfähigkeit des Werkzeugs gibt. Die Untersuchungen in diesem Beitrag beschränken sich auf einphasige Strömungen in kreisförmigen Querschnitten und geraden Kanalgeometrien. Als repräsentatives Anwendungsbeispiel für eine Werkzeugmaschine wird die Kühlung eines einfachen Spritzgießwerkzeugs untersucht. Die durchgeführten Analysen zeigen, dass der Einsatz von statischer Mischelemente zur Verbesserung der Wärmeübertragung sehr effektiv ist, insbesondere bei Strömungen mit niedrigen bis mittleren Reynoldszahlen, konturnaher Kühlung, hohen Wärmestromwerten sowie hoher Wärmeleitfähigkeit des Werkzeugmaterials. / In this contribution, the effectiveness of helical static mixers in different arrangements and flow configurations/regimes is explored. By means of a thorough numerical analysis the application limits of helical static mixers for the heat transfer enhancement inside cooling channels of machine tools is provided. The numerical simulations were processed with the commercial finite volume Computational Fluid Dynamics (CFD) code, ANSYS Fluent 2020 R2. This study shows that there exists an optimal range of application for static mixers as heat exchange intensifier depending on the flow speed, the transmitted heat flow and the thermal conductivity of the tool. The investigations of this contribution are restricted to single-phase flow in circular cross-sections and straight channel geometries. As a representative application example for a machine tooling, the cooling of a simple injection mould is investigated. The research carried out reveals that the application of static mixing elements for enhancement of heat transfer is very effective, particularly for fluid flow with low to medium Reynolds numbers, close-contour cooling, high values of heat fluxes as well as high thermal conductivity of the tooling material.

Flow-induced vibration caused by fully developed pipe flow has been recognized, but not fully investigated under turbulent conditions. This thesis focuses on the development of a numerical Fluid-Structure Interaction (FSI) model that will help define the relationship between pipe wall vibration and the physical characteristics of turbulent flow. Commercial FSI software packages are based on Reynolds Averaged Navier-Stokes (RANS) fluid models, which do not compute the instantaneous fluctuations in turbulent flow. This thesis presents an FSI approach based on Large Eddy Simulation (LES) flow models, which do compute the instantaneous fluctuations in turbulent flow. The results based on the LES models indicate that these fluctuations contribute to the pipe vibration. It is shown that there is a near quadratic relationship between the standard deviation of the pressure field on the pipe wall and the flow rate. It is also shown that a strong relationship between pipe vibration and flow rate exists. This research has a direct impact on the geothermal, nuclear, and other fluid transport industries.

[ES] El interés en reducir el peso y resistencia aerodinámica de vehículos y en desarrollar fuentes de energía renovables se ha incrementado debido a la compleja situación ambiental y los requerimientos legales para reducir las emisiones de contaminantes y el consumo de combustibles. La industria aeronáutica ha propuesto nuevos diseños que integren conceptos como alas de alto alargamiento y materiales con elevada resistencia específica, como los materiales compuestos. Por su parte, conceptos similares se emplean en la generación de energía eólica. El radio de las palas de las turbinas eólicas se incrementa paulatinamente, siendo un ejemplo muy claro las grandes instalaciones off-shore. El uso de estructuras más alargadas y ligeras provoca mayor deformación debida a las cargas aerodinámicas. Este fenómeno se conoce como aeroelasticidad y combina los efectos de las cargas aerodinámicas, los efectos inerciales y las tensiones internas de la estructura. La combinación de las cargas anteriores provoca fenómenos de amortiguamiento de las vibraciones, o por el contrario, inestabilidades aeroelásticas. Diferentes metodologías pueden ser empleadas para simular los fenómenos aeroelásticos. La metodología más extendida para la simulación de las ecuaciones elásticas del sólido es la conocida como análisis de elementos finitos. Respecto a las ecuaciones de conservación del fluido, la mecánica de fluidos computacional es la herramienta de resolución para un problema arbitrario. La combinación de las metodologías anteriores puede ser empleada para el cálculo de fenómenos aeroelásticos. Sin embargo, el coste computacional de estas simulaciones es inasumible en la mayoría de casos de aplicación. Se requiere una metodología nueva capaz de reducir el coste de cálculo. Este trabajo se centra en el desarrollo de modelos de orden reducido que permitan resolver el problema acoplado sin pérdidas sustanciales de precisión. En primer lugar, la estructura tridimensional se reduce a una sección equivalente que reproduzca la física del sólido original. La sección equivalente se acopla con dos modelos aerodinámicos: simulaciones de mecánica de fluidos computacional y un modelo reducido basado en redes neuronales. Ambos modelos presentan elevada precisión respecto a las simulaciones tridimensionales. Sin embargo, algunos efectos como los efectos aerodinámicos tridimensionales, las distribuciones de carga aerodinámica, la presencia de materiales ortotrópicos y los acoplamientos estructurales no pueden ser simulados. Con el objetivo de resolver los limitantes del modelo anterior, se propone un segundo modelo de orden reducido. En este caso se trata de un algoritmo basado en elementos de viga. El algoritmo se diseña para ser capaz de incluir el cálculo de materiales ortotrópicos y diferentes tipos de problemas aeroelásticos. Inicialmente, se emplea el software para determinar su precisión en el cálculo de una viga de material compuesto y sección rectangular. Estos resultados se validan con las simulaciones tridimensionales. De este modo se demuestra la capacidad de la herramienta computacional para predecir las inestabilidades y los efectos de acoplamiento estructural provocados por la orientación de las fibras. Posteriormente, el algoritmo se emplea en la simulación de turbinas eólicas, mejorando los rangos de operación de las palas sin que ello suponga una penalización desde el punto de vista del peso de la misma. Finalmente, un ala basada en una estructura de membrana resistente es simulada. El cálculo obtiene una gran precisión en la predicción de la velocidad de flameo respecto a la simulación acoplada, siendo la única limitación del modelo la predicción de la distorsión de la membrana. El trabajo presente un conjunto de modelos de orden reducido que permiten disminuir el coste computacional de las simulaciones aeroelásticas en órdenes de magnitud. También, se proporcionan directrices para la selección del modelo reducido apropiado para los casos de interés. / [CA] L'interès a reduir el pes i la resistència aerodinàmica dels vehicles i a desenvolupar fonts d'energia renovables s'ha incrementat a causa de la complexa situació ambiental i els requeriments legals per a reduir les emissions de contaminants i el consum de combustibles. La indústria aeronàutica ha proposat nous dissenys que integren conceptes com ales d'alt allargament i materials amb elevada resistència específica, com ara els materials compostos. Per la seua banda, conceptes similars es fan servir en la generació d'energia eòlica. El radi de les pales de les turbines eòliques s'incrementa progresivament, sent un exemple molt clar les grans instal·lacions off-shore. L'ús d'estructures més allargades i lleugeres provoca més deformació deguda a les càrregues aerodinàmiques. Aquest fenomen es coneix com a aeroelasticitat i combina els efectes de les càrregues aerodinàmiques, els efectes inercials i les tensions internes de l'estructura. La combinació de les càrregues anteriors provoca fenòmens d'esmorteïment de les vibracions, o per contra, inestabilitats aeroelàstiques. Diferents metodologies poden ser emprades per simular els fenòmens aeroelàstics. La metodologia més estesa per a la simulació de les equacions elàstiques del sòlid és la coneguda com a anàlisi d'elements finits. Pel que fa a les equacions de conservació del fluid, la mecànica de fluids computacional és l'eina de resolució per a un problema arbitrari. La combinació de les metodologies anteriors pot ser emprada per al càlcul de fenòmens aeroelàstics. Tot i això, el cost computacional d'aquestes simulacions és inassumible en la majoria de casos d'aplicació. Cal una metodologia nova capaç de reduir el cost de càlcul. Aquest treball se centra en el desenvolupament de models d'ordre reduït que permeten resoldre el problema acoblat sense pèrdues substancials de precisió. En primer lloc, l'estructura tridimensional es reduix a una secció equivalent que reproduixca la física del sòlid original. La secció equivalent s'acobla amb dos models aerodinàmics. El primer empra les forces aerodinàmiques obtingudes mitjançant simulacions de mecànica de fluids computacional. Posteriorment es fa servir un model reduït basat en xarxes neuronals. Tots dos models presenten elevada precisió respecte a les simulacions tridimensionals. No obstant això, alguns efectes com ara els efectes aerodinàmics tridimensionals, les distribucions de càrrega aerodinàmica, la presència de materials ortotròpics i els acoblaments estructurals no poden ser simulats. Amb l'objectiu de resoldre els limitants del model anterior, es proposa un segon model dordre reduït. En aquest cas és un algorisme basat en elements de biga. L'algorisme es dissenya per ser capaç d'incloure el càlcul de materials ortotròpics i diferents tipus de problemes aeroelàstics. Inicialment, s'empra el programari per determinar-ne la precisió en el càlcul d'una biga de material compost i secció rectangular. Aquests resultats es validen amb les simulacions tridimensionals. D'aquesta manera, es demostra la capacitat de l'eina computacional per predir les inestabilitats i els efectes d'acoblament estructural provocats per l'orientació de les fibres. Posteriorment, l'algorisme s'empra en la simulació de turbines eòliques, millorant els rangs d'operació de les pales sense que això suposi una penalització des del punt de vista del pes. Finalment, una ala basada en una estructura de membrana resistent és simulada. El càlcul obté una gran precisió en la predicció de la velocitat de flameig respecte a la simulació acoblada, i l'única limitació del model és la predicció de la distorsió de la membrana. El treball presenta un conjunt de models reduïts que permeten disminuir el cost computacional de les simulacions aeroelàstiques en ordres de magnitud. També es proporcionen directrius per a la selecció del model reduït adequat per als casos d'interès. / [EN] The complex environmental situation and the legal requirements for decreasing pollutant emissions and fuel consumption have increased the interest in reducing the empty weight and drag of vehicles and developing renewable energy sources. Due to the former, the aviation industry has proposed new designs integrating high strength-to-weight ratios, such as composite materials and higher aspect ratio wings. These increases in aspect ratio have also been applied to wind energy generation. The rotors of wind turbines are increasing their diameters in recent years: a clear example is the massive off-shore facilities. Using larger and lightweight structures increases the effects of the aerodynamic loads on structural deformation. Structural dynamics are strongly connected to the air-structure interaction. This phenomenon, called aeroelasticity, combines the effect of the external aerodynamic loads, the inertial forces, and the internal elastic stress of the structure. The complex combination of all the previous effects may damp the vibrations of the structure, or on the contrary, they could increase their amplitude, resulting in an unstable phenomenon. The simulation of the aeroelastic phenomena can be performed using different approaches. The well-known finite element analysis is the most extended methodology for solving solid elastic equations. Regarding fluid conservation equations, computational fluid dynamics is the principal tool for resolving general aerodynamic problems. The aeroelastic simulations can be calculated by combining the previous algorithms. Nevertheless, the computational cost of these methodologies is excessive for a general engineering case. Therefore, new methodologies are required. This work focuses on developing aeroelastic reduced-order models that compute the coupled phenomena without substantial accuracy losses. Initially, the complete three-dimensional structure is reduced to an equivalent section that reproduces the structure. The equivalent structural section is coupled with two aerodynamic models. The first one uses the forces calculated with aeroelastic computational fluid dynamics. Then, a surrogate model based on artificial neural networks is combined with the equivalent section. Both models show accurate agreement compared to the complete three-dimensional simulations in predicting unstable velocity. However, the three-dimensional aerodynamic effects, load distribution, orthotropic materials, and structural couplings cannot be considered. In order to solve the previous limitations, a reduced-order model based on a beam element solver is proposed. The algorithm is designed to consider a general orthotropic material and different typologies of aeroelastic problems. Initially, the software is proven to simulate accurately a squared cross-section composite material beam. The results are validated with the complete three-dimensional simulations, demonstrating the capabilities of the tool for predicting the instabilities and the effects of the fiber orientations. Then, the algorithm is used for simulating a wind turbine blade, and the algorithm results are used to improve the operation range of the blades without weight penalties. Finally, a resistant membrane wing is simulated, obtaining high accuracy in the prediction of the flutter velocity compared with the complete coupled simulation. In addition, the only limitation of the model is the prediction of the membrane distortion. The work presents a set of reduced-order models that allow for reducing the computational cost of the aeroelastic simulations by orders of magnitude. In addition, a decision pattern is provided for selecting the appropriate algorithm for the interest problem. / This thesis have been funded by Spanish Ministry of Science, Innovation and University through the University Faculty Training (FPU) program with reference FPU19/02201. / Cremades Botella, A. (2023). Fluid-structure interaction with the application to the non-linear aeroelastic phenomena [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/199249

Modelling the full event of an underwater explosion (UNDEX) is complex and requires advanced modelling methods in order to achieve accurate responses. The process of an UNDEX includes a series of events that has to be considered. When a detonation is initiated, a shock-wave propagates and the rest products from the explosive material creates a gaseous bubble with high pressure which pulsates and impacts the surroundings. Reflections of the initial shock-wave can also appear if it hits the sea floor, water surface or other obstacles. There are different approaches how to numerically model the impact of an UNDEX on a structure, some with analytical approaches without a water domain and others where a water domain has to be modelled. This master’s thesis focuses on two modelling methods that are available in the finite element software LS-DYNA. The simpler method is called Sub-Sea Analysis (SSA) and does not require a water domain, thus it can be beneficial to use in an early design stage, or when only approximated responses are desired. To increase the accuracy, a more complex method called S-ALE can be used. By implementing this method, the full process of an UNDEX can be studied since both the fluid domain and explosive material are meshed. These methods are studied separately together with a combination of them. Another important aspect to be considered is that oscillations of a structure submerged in water differs from the behavior it has in air. Depending on the numerical method used, the impact of the water can be included. Natural frequencies of structures submerged in water are studied, how it changes and how the methods takes this into account. To verify the numerical models, experiments were executed with a cylindrical test object where the distance and weight of charge were altered through out the test series. It was found that multiple aspects affects the results from the experiments, that are not captured in the numerical models. These aspects have for instance to do with reflections, how accurate the test object is modelled and the damping effects of the water. It is concluded that the numerical models are sensitive when small charges and fragile structures are studied. High frequency oscillations were not triggered in the experiment but found for both methods. It should be further investigated if the methods are more accurate for larger charges and stronger structures. Experiments with larger water domain would also be beneficial to reduce effects from reflections, as well as a more accurate model of the cylinder in the simulations.

<p>Positive displacement machines (PDMs) operate based on the principle of positive displacement, which necessitates a periodic alteration of volume. This volume variation is accomplished through relative motion between machine components. PDMs find extensive applications in diverse domains, encompassing fluid power systems, lubrication systems, fluid transport systems, fuel injection systems, and more. The primary distinction among PDMs lies in the geometric mechanisms employed for fluid displacement, as well as the flow distribution mechanisms they employ. PDMs can be broadly classified into piston machines, vane machines, screw machines, and gear machines. In fluid power systems, the most commonly used PDMs are the piston and gear machines. Piston machines can be further classified into radial piston machines, in-line piston machines, and axial piston machines. The most commonly used piston machines are the axial piston machine owing to their superior efficiency and compactness. Gear machines can be further classified into external gear machines, internal gear machines, and annular gear machines. The most commonly used gear machine is the external gear machine owing to its price.</p> <p><br></p> <p>PDMs typically involve multiple solid bodies in relative motion, with micron-level gaps between them. These gaps, known as lubricating interfaces, present a significant design challenge during the machine development process. They are a primary source of power losses and play a crucial role in determining the efficiency and durability of the machine. The lubricating interfaces must effectively balance loads and maintain a high-pressure fluid seal. Achieving this delicate balance necessitates a comprehensive understanding of the underlying physical phenomena. Lubricating interfaces generate substantial heat due to viscous dissipation, which directly impacts the operation of the entire machine. The viscosity of the working fluid rapidly decays with temperature, causing the warmer fluid within the lubricating interface to possess lower viscosity. Consequently, it can support lesser loads and is more prone to leakage. Moreover, as the solid bodies enclosing the warmer fluid heat up, they undergo thermal expansion, further changing the clearance and leading to a decline in performance. Additionally, the elevated temperature of the fluid within the lubricating interface affects the compressibility of the displacement chamber fluid, thereby influencing the pressurization characteristics of the entire unit. Thus, thermal effects play a critical role in the performance of PDMs.</p> <p><br></p> <p>  The ever-increasing market demand for more compact, efficient, and reliable designs requires a continuous process of design improvements over previous designs, and sometimes completely new designs. Sophisticated simulation tools are a necessity for such a design process. Additionally, these simulation tools also prove to be valuable in formulating design modifications in case of underperforming designs. Due to the complexity associated with the operation of such units, the simulation tools need to capture a wide variety of physical phenomena. Over the past few decades, owing to the increasing computing power of the desktop computer, several simulation tools have been proposed across the literature to aid the design process of such machines with each having limitations of their own.</p> <p><br></p> <p>  The objective of the present thesis is to propose a modeling approach that assists in the design process of positive displacement machines, addressing various limitations identified in the existing literature. The approach is intentionally designed to be generic, enabling its application across a diverse range of positive displacement machines. The modeling approach encompasses three distinct domains: the displacement chamber fluid domain, the lubricating interface fluid domain, and the solid domain. A novel thermal model that integrates all three domains is introduced. </p> <p><br></p> <p>  To validate the effectiveness of the proposed modeling approach, two separate validation studies are conducted. The first study focuses on a model for an isolated piston/cylinder interface of an axial piston machine, operating under the mixed lubrication regime. The model demonstrates a strong agreement with the measured data. The second study involves steady-state measurements of an entire axial piston machine. The model is validated by comparing the steady-state flow characteristics and temperature distribution on the valveplate, both of which are accurately captured by a single fully coupled model. The modeling approach developed in this study, specifically, the energy conservation in the lubricating interface, heat transfer in the solid bodies, and thermal deformation in the solid bodies are all generalized for applicability in different types of PDMs. However, the results presented in this thesis pertain to an axial piston machine.</p>

<p>This thesis is concerned with a theoretical and experimental investigation of a duckbill valve (DBV). Duckbill valves are non-return valves made of a composite material, which deforms to open the valve as the upstream pressure increases. The head-discharge behavior is a fluid-structure interaction (FSI) problem since the discharge depends on the valve opening that in turn depends on the pressure distribution along the valve produced by the discharge. To design a duckbill valve, a theoretical model is required, which will predict the head-discharge characteristics as a function of the fluid flow through the valve and the valve material and geometry.</p> <p>The particular valves of concern in this study, which can be very large, are made from laminated, fiber-reinforced rubber. Thus, the structural problem has strong material as well as geometric nonlinearities due to large deflections. Clearly, a fully coupled FSI analysis using three-dimensional viscous flow would be very challenging and therefore, a simplified approach was sought that treats the essential aspects of the problem in a tractable way. For this purpose, the DBV was modeled using thick shell finite elements, which included the laminates of hyperelastic rubber and orthotropic fabric reinforcement. The finite element method (FEM) was simplified by assuming that the arch side edges of the valve were clamped. The unsteady 1D flow equation was used to model the ideal fluid dynamics that enabled a full FSI analysis. Moreover, verification for the ideal flow was carried out using a transient, Reynolds-averaged Navier-Stokes finite volume solver for the viscous flow corresponding to the deformed valve predicted by the simplified FSI model.</p> <p>In order to validate the predictions of the FSI simulations, an experimental study was performed at several mass flow rates. Pressure drops along the water tunnel, valve inlet and outlet velocity profiles were measured, as well as valve opening deformations as functions of upstream pressures.</p> <p>Additionally, the valve deformations under various back pressures were analyzed when the downstream pressure exceeded the upstream pressure using the layered shell model without coupling and with simplified boundary constraints to avoid solving the contact problem for the inward-deformed duckbill valve. Flow-induced vibration (FIV) of the valve at small openings was also examined to improve our understanding of the valve stability behaviour. Some interesting valve oscillation phenomena were observed.</p> <p>Conclusions are drawn regarding the FSI model on the predictions and comparisons with the experimental results. The transient 1D flow equation has been demonstrated to adequately model the fluid dynamics of a duckbill valve, largely due to the fact that viscous effects are negligible except when the valve is operating at very small openings. Fiber reinforcement of the layered composite rubber was found to play an important role in controlling duckbill valve material stretch, especially at large openings. The model predicts oscillations at small openings but more research is required to better understand this behaviour.</p> / Doctor of Philosophy (PhD)

<p dir="ltr">Positive displacement machines are used in various industries spanning the power spectrum, from industrial robotics to heavy construction equipment to aviation. These machines should be highly efficient, compact, and reliable. It is very advantageous for designers to use virtual simulations to design and improve the performance of these units as they significantly reduce cost and downtime. The recent trends of electrification and the goal to increase power density force these units to work at higher pressures and higher rotational speeds while maintaining their efficiencies and reliability. This push means that the simulation models need to advance to account for various aspects during the operation of these machines. </p><p dir="ltr">These machines typically have several bodies in relative motion with each other. Quantifying these motions and solving for their effect on the fluid enclosed are vital as they influence the machine's performance. The push towards higher rotational speeds introduces unwanted cavitation and aeration in these units. To model these effects, keeping the design evaluation time low is key for a designer. The lumped parameter approach offers the benefit of computational speed, but a major drawback that comes along with it is that it typically assumes fluid inertia to be negligible. These effects cannot be ignored, as quantifying and making design considerations to negate these effects can be beneficial. Therefore, this thesis addresses these key challenges of cavitation dynamics, body dynamics, and accounting for fluid inertia effects using a lumped parameter formulation.</p><p dir="ltr">To account for dynamics features related to cavitation, this thesis proposes a novel approach combining the two types of cavitation, i.e., gaseous and vaporous, by considering that both vapor and undissolved gas co-occupy a spherical bubble. The size of the spherical bubble is solved using the Rayleigh-Plesset equation, and the transfer of gas through the bubble interface is solved using Henry's Law and diffusion of the dissolved gas in the liquid. These equations are coupled with a novel pressure derivative equation. To account for body dynamics, this thesis introduces a novel approach for solving the positions of the bodies of a hydraulic machine while introducing new methods to solve contact dynamics and the application of Elasto Hydrodynamic Lubrication (EHL) friction at those contact locations. This thesis also proposes strategies to account for fluid inertia effects in a lumped parameter-based approach, taking as a reference an External Gear Machine. This thesis proposes a method to study the effects of fluid inertia on the pressurization and depressurization of the tooth space volumes of these units. The approach is based on considering the fluid inertia in the pressurization grooves and inside the control volumes with a peculiar sub-division. Further, frequency-dependent friction is also modeled to provide realistic damping of the fluid inside these channels.</p><p dir="ltr">To show the validity of the proposed dynamic cavitation model, the instantaneous pressure of a closed fluid volume undergoing expansion/compression is compared with multiple experimental sources, showing an improvement in accuracy compared to existing models. This modeling is then further applied to a gerotor machine and validated with experiments. Integrating this modeling technique with current displacement chamber simulation can further improve the understanding of cavitation in hydraulic systems. Formulations for body dynamics are tested on a prototype Gerotor and Vane unit. For both gerotor and vane units, comparisons of simulation results to experimental results for various dynamic quantities, such as pressure ripple, volumetric, and hydromechanical efficiency for multiple operating conditions, have been done. Extensive validation is performed for the case of gerotors where shaft torque ripple and the motion of the outer gear is experimentally validated. The thesis also comments on the distribution of the different torque loss contributions. The model for fluid inertia effects has been validated by comparing the lumped parameter model with a full three-dimensional Navier Stokes solver. The quantities compared, such as tooth space volume pressures and outlet volumetric flow rate, show a good match between the two approaches for varying operating speeds. A comparison with the experiments supports the modeling approach as well. The thesis also discusses which operating conditions and geometries play a significant role that governs the necessity to model such fluid inertia effects in the first place.</p>