Tese de mestrado integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 2009

The purpose of this study was to investigate the velocity distribution through an annular bed packed randomly with equal sized spheres. Extensive research has been conducted on the velocity distribution inside packed beds packed with equal sized spheres, different sized spheres, deformed spheres, cylinders and Raschig-rings. A majority of these experimental and numerical studies focused on the cylindrical packed bed. These studies and numerical models are all confined to the velocity profile once the fluid flow is fully developed. The development of the velocity through the inlet region of the bed and the fluid flow redistribution in the outlet of the bed is thus neglected. The experimental investigation into the velocity distribution down stream of the annular packed bed of the HTTU indicated that the velocity profile was independent of the mass flow rate for a particle Reynolds number range of 439 £ Re £ 3453 . These velocity profiles did not represent the distribution of the axial velocity due to shortcomings associated with the single sensor hot wire anemometry system used to measure the velocity distribution. A numerical investigation, using the RANS CFD code STAR-CCM+®, into the velocity distribution downstream of an explicitly modelled bed of spheres indicated that the axial velocity distribution could be extracted from the experimental velocity profiles by using an adjustment factor of 0.801. This adjusted velocity profile was used in the verification of the implicit bed simulation model. The implicit bed simulation model was developed in STAR-CCM+®. The resistance of the spheres was modelled using the KTA (1981) pressure drop correlation and the structure of the bed was modelled using the porosity correlation proposed by Martin (1978), while the effective viscosity model of Giese et al. (1998), adjusted by a factor of 0.8, was used to model the velocity distribution in the near wall region. It was found that the structure in the inlet region of the bed, where two walls disturb the packing structure, can be modelled as the weighted average of the radial and axial porosity while the structure in the outlet regions can be modelled by letting the radial porosity increase linearly to unity. The basic shape of the velocity profile is established immediately when the fluid enters the bed. The amplitude of the velocity peaks however increase in magnitude until the velocity profile is fully developed at a distance approximately of five sphere diameters from the bed inlet. The profile remains constant throughout the bed until the outlet region of the bed is reached. In the outlet region a significant amount of fluid redistribution is observed. The amplitude of the velocity peaks is reduced and the position of the velocity peaks is shifted inwards towards the centre of the annular region. The fully developed velocity profile, predicted by the simulation model is in good agreement with profiles presented by amongst others Giese et al. (1998). The current model however also offers insight into the development of the profile through the inlet of the bed and the fluid redistribution, which occurs in the outlet region of the bed. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2010.

The purpose of this study was to investigate the velocity distribution through an annular bed packed randomly with equal sized spheres. Extensive research has been conducted on the velocity distribution inside packed beds packed with equal sized spheres, different sized spheres, deformed spheres, cylinders and Raschig-rings. A majority of these experimental and numerical studies focused on the cylindrical packed bed. These studies and numerical models are all confined to the velocity profile once the fluid flow is fully developed. The development of the velocity through the inlet region of the bed and the fluid flow redistribution in the outlet of the bed is thus neglected. The experimental investigation into the velocity distribution down stream of the annular packed bed of the HTTU indicated that the velocity profile was independent of the mass flow rate for a particle Reynolds number range of 439 £ Re £ 3453 . These velocity profiles did not represent the distribution of the axial velocity due to shortcomings associated with the single sensor hot wire anemometry system used to measure the velocity distribution. A numerical investigation, using the RANS CFD code STAR-CCM+®, into the velocity distribution downstream of an explicitly modelled bed of spheres indicated that the axial velocity distribution could be extracted from the experimental velocity profiles by using an adjustment factor of 0.801. This adjusted velocity profile was used in the verification of the implicit bed simulation model. The implicit bed simulation model was developed in STAR-CCM+®. The resistance of the spheres was modelled using the KTA (1981) pressure drop correlation and the structure of the bed was modelled using the porosity correlation proposed by Martin (1978), while the effective viscosity model of Giese et al. (1998), adjusted by a factor of 0.8, was used to model the velocity distribution in the near wall region. It was found that the structure in the inlet region of the bed, where two walls disturb the packing structure, can be modelled as the weighted average of the radial and axial porosity while the structure in the outlet regions can be modelled by letting the radial porosity increase linearly to unity. The basic shape of the velocity profile is established immediately when the fluid enters the bed. The amplitude of the velocity peaks however increase in magnitude until the velocity profile is fully developed at a distance approximately of five sphere diameters from the bed inlet. The profile remains constant throughout the bed until the outlet region of the bed is reached. In the outlet region a significant amount of fluid redistribution is observed. The amplitude of the velocity peaks is reduced and the position of the velocity peaks is shifted inwards towards the centre of the annular region. The fully developed velocity profile, predicted by the simulation model is in good agreement with profiles presented by amongst others Giese et al. (1998). The current model however also offers insight into the development of the profile through the inlet of the bed and the fluid redistribution, which occurs in the outlet region of the bed. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2010.

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Práce se zabývá výzkumem v oblasti odmrazování světlometu. Jejím cílem je vytvoření numerického simulačního modelu, který dokáže předpovídat průběh odmrazování, zároveň tak může odhalit nedostatky při návrhu světlometu. Na simulační modelu jsou testovány proměnlivé parametry, výsledkem práce je nalezení optimálních podmínek, které zajistí validní výsledky simulace při současné úspoře výpočetního času.

The vehicle body was measured by using ATOS 3D scanner. Measured data from the ATOS 3D scanner were applied to make a 3D model of vehicle body and to make a 3D model of whole vehicle by using computer program Pro/ENGINEER. The model of vehicle was made with a view for future use of CAD model. Surface of the vehicle model was used for computation of vehicle aerodynamics – aerodynamic static pressure distribution by using CFD software Star-CCM+.

Master’s thesis deals with the aerodynamics of racing vehicle for various settings of clearance and tilt of body. First is described the theory of aerodynamics and flow. It was necessary to build the CAD model of racing car for analysis. Assembly of this model is the next chapter of the master’s thesis. This is followed by CFD analysis, where is displayed a simplified model of the vehicle. This part describes the overall process and setting in the CFD program. In conclusion, the results are summarized for each setting.

Wading is the phenomenon where a vehicle drives through water with a relatively deep water level. Sincea large portion of the vehicle is submerged in water it can affect the driveability and function of individualcomponents. Wading is therefore an important phenomenon to be aware of especially today where society moves towards alternative energy sources. This includes water sensitive components when contact with water can generate major consequences. Previous knowledge and experience of wading has been from performing physical tests, but using Computational Fluid Dynamics (CFD) to examine the phenomenon can accelerate the iterative design process. In this thesis, numerical method of wading simulations on complete heavy-duty vehicles using the software STAR-CCM+ are developed. Furthermore, the results from the numerical methods are validated against results from physical tests performed at Scania’s test facility in Södertälje. The numerical methods are divided into a simplified model of a Battery Electric Vehicle (BEV) and a detailed geometry of a gas-driven vehicle from Scania. Beside dividing the wading scenario into the geometries, two different methods are developed, Wave and Wading. The Wave-method includes the vehicle standing still while a water wave is fed in through the inlet of the domain, i.e. allowed to flush over the vehicle, with a velocity of 3.6 km/h and 8 km/h. This method is implemented for both a generic simplified BEV truck and a detailed real-life Scania truck. For the Wading-method, motion is applied to the vehicle where itis driving with a velocity of 3.6 km/h through a digital twin of the water trench available at the test facility. This method is further divided into two cases, Zero Gap and Floating, where the difference is the distance between the tires of the vehicle and ground of the domain. The Floating-case includes a 10 cm distance and the Zero Gap-case has no gap between the tires and ground. The Wading-method is only implemented for the simplified geometry due to the computational cost and complexity. All methods use the Volume of Fluid (VOF) method for multiphase modelling and the Zero Gap-case uses Overset Mesh for modelling motion. The validation of the simulations focuses on the water behaviour such as water surface topology and water flowing inside the vehicle while wading. The results for the Wave-method with both the simplified and detailed truck at 8 km/h shows similarities in the water surface topology between the numerical model and the physical test. The simulations of the Wading-method is not visualising any similarities since the visible wave pattern are few and unclear in the numerical model. An isosurface is used to visualise the surface of the water which generated a smooth topology since no other options, such as vector fields, are added. It is found that the water movement inside the vehicle will affect water sensitive areas, e.g. on the battery packs. It is concluded that the derived methods are a first draft and should be directed towards future development in optimising the methods to lower the computational cost, but also to improve the capturing of the interface between the two phases. Due to instability and computational cost the detailed geometry is not implemented in the Wading-method. The methods are adapted to use different vehicle types since the simplified and detailed geometry are a BEV and a gas-driven truck respectively.

Experimental tests on a transonic annular rig are time-consuming and expensive, so it is desirable to use experimental results to validate a computational model which can then be used to extract much more information. The purpose of this work is to create a numerical model that can be used to simulate many different scenarios and then to apply these results to experimental data.; In the modern world, gas turbines are widely used in aircraft propulsion and electricity generation. These applications represent a massive use of energy worldwide, so even a very small increase in efficiency would have a significant beneficial economic and environmental impact. There are many ways to optimize the operation of a gas turbine, but a fundamental approach is to increase the turbine inlet temperature to increase the basic thermodynamic efficiency of the turbine. However, these temperatures are already well above the melting temperature of the components. A primary cooling methodology, called film cooling, creates a blanket of cool air over the surface and is an effective way to help protect these components from the hot mainstream gasses. This paper focuses on the effect of the film holes upstream of the first row of blades in the turbine because this is the section that experiences the highest thermal stresses. Many factors can determine the effectiveness of the film cooling, so a complete understanding can lead to effective results with the minimum flow rate of coolant air. Many studies have been published on the subject of film cooling, but because of the difficulty and expense of simulating turbine realistic conditions, many authors introduce vast simplifications such as low speed conditions or linear cascades. These simplifications do not adequately represent the behavior of a turbine and therefore their results are of limited use. This study attempts to eliminate many of those simplifications. The test rig used in this research is based on the NASA-GE E³ design, which stands for Energy Efficient Engine. It was introduced into the public domain to provide an advanced platform from which open-literature research could be performed.

This thesis investigates the capabilities of STAR-CCM+, a Computational Fluid Dynamics (CFD) software owned by Siemens, in predicting hypersonic heat transfer loads on forward-facing surfaces. Results show that STAR-CCM+ predicted peak heat transfer loads within +/- 20% of experimental data on the leading edge of a delta wing design from the X-20 Dyna-Soar program with 73o of sweep. Steady-state laminar simulations were run as replications of wind tunnel tests documented in NASA CR-535, a NASA technical report that measured and studied the hypersonic pressure and heat transfer loads on preliminary X- 20 wing designs across a wide range of Reynolds numbers and Mach numbers in different wind tunnel and shock tunnel facilities. One of the Mach 8.08 test cases that was run at NASA Arnold Engineering Development Center Wind Tunnel B was selected as the case of comparison for this thesis, which was designated as test AD462M-1 in the original report. The CFD simulations assumed an ideal gas in laminar flow with temperature-dependent viscosity, thermal conductivity, and isobaric specific heat across an angle of attack range from 0o to 30o. A separate CFD study of heat transfer loads of a hemisphere-cylinder at Mach 6.74 was used as a simpler and less computationally-expensive validation case compared against wind tunnel data from NASA Langley Research Center to help select the appropriate CFD solver and mesh settings for this thesis. For the hemisphere-cylinder, the heat transfer load at the stagnation point was overpredicted in STAR-CCM+ by 21.8%. Peak heat transfer loads on the delta wing leading edge were all within +/- 20% of the wind tunnel data, which was published for angles of attack between 15o to 30o. A more adverse heat transfer gradient along the leading edge of the delta wing was also observed in the direction from the front of the wing to the outer wing tip when compared to wind tunnel data. The pressure loads on the delta wing leading edge in CFD were within +/-10% of wind tunnel measurements.