scholarly journals Stall mitigation using wing spoilers

2021 ◽  
Author(s):  
Harpuneet Kaur Pabla
Keyword(s):  
Turbulence Model ◽  
Leading Edge ◽  
Independent Study ◽  
Performance Study ◽  
Baseline Study ◽  
Sst Turbulence Model ◽  
Aircraft Performance ◽  
Experimental Values ◽  
Unsteady Effects ◽  
Performance Results

The objective of this thesis was to conduct a two dimensional Compuational Fluid Dyanmic analysis on wing-spoiler lift effectiveness in delaying stall effects using the NACA 2412 airfoil section. The project was divided into three sub-areas; grid-independent study, the baseline study and spoiler performance study. The grid independent study was carried out for the purpose of mesh optimization, i.e. to determine the point at which computed solutions had little or no change in value with increasing number of mesh nodes. This study was conducted at an angle of attack of 16 degrees as it served as both a high pitch angle value as well as a pre-stall point in which unsteady effects were not a determining influence that may have served as a deterrent in resolving potential grid error. The baseline study was conducted to establish a data foundation to be used as a comparison to the spoiler study to effectively determine its effects on the lift performance. Results for the baseline study were shown to match experimental values most closely using the Transition SST Turbulence Model at a Mach number of 0.17. Therefore to remain consistent the spoiler study was carried out for the same Mach value with the viscosity of 1.84E-5 [kg/ms] and Temperature of 300 [K], which produced a Reynolds number of approximately 3.79E6. Therefore, using the same flight conditions employed in the baseline study, the spoiler grids were generated in ANSYS ICEM CFD and imported into Fluent and solved using the Transition SST turbulence model. Results for spoiler deflections of 4, and 10 degrees were carried out across spoiler locations of 60%, 65 and 70% leading edge chord-wise locations. Results were shown to be optimal for 4 degree spoiler deflections across all locations tested, with highest values for lift effectiveness recorded at 70% leading edge. The findings of this thesis provides much potential for utilizing spoilers as lift enhancing devices and adds an alternate perspective in improving aircraft performance.

scholarly journals Stall mitigation using wing spoilers

2021 ◽  
Author(s):  
Harpuneet Kaur Pabla
Keyword(s):  
Turbulence Model ◽  
Leading Edge ◽  
Independent Study ◽  
Performance Study ◽  
Baseline Study ◽  
Sst Turbulence Model ◽  
Aircraft Performance ◽  
Experimental Values ◽  
Unsteady Effects ◽  
Performance Results

The objective of this thesis was to conduct a two dimensional Compuational Fluid Dyanmic analysis on wing-spoiler lift effectiveness in delaying stall effects using the NACA 2412 airfoil section. The project was divided into three sub-areas; grid-independent study, the baseline study and spoiler performance study. The grid independent study was carried out for the purpose of mesh optimization, i.e. to determine the point at which computed solutions had little or no change in value with increasing number of mesh nodes. This study was conducted at an angle of attack of 16 degrees as it served as both a high pitch angle value as well as a pre-stall point in which unsteady effects were not a determining influence that may have served as a deterrent in resolving potential grid error. The baseline study was conducted to establish a data foundation to be used as a comparison to the spoiler study to effectively determine its effects on the lift performance. Results for the baseline study were shown to match experimental values most closely using the Transition SST Turbulence Model at a Mach number of 0.17. Therefore to remain consistent the spoiler study was carried out for the same Mach value with the viscosity of 1.84E-5 [kg/ms] and Temperature of 300 [K], which produced a Reynolds number of approximately 3.79E6. Therefore, using the same flight conditions employed in the baseline study, the spoiler grids were generated in ANSYS ICEM CFD and imported into Fluent and solved using the Transition SST turbulence model. Results for spoiler deflections of 4, and 10 degrees were carried out across spoiler locations of 60%, 65 and 70% leading edge chord-wise locations. Results were shown to be optimal for 4 degree spoiler deflections across all locations tested, with highest values for lift effectiveness recorded at 70% leading edge. The findings of this thesis provides much potential for utilizing spoilers as lift enhancing devices and adds an alternate perspective in improving aircraft performance.

Applicability of Turbulence Models on Characteristics Prediction of Centrifugal Pumps

2011 ◽  
Author(s):  
Yong Wang ◽  
Houlin Liu ◽  
Shouqi Yuan ◽  
Minggao Tan ◽  
Minhua Shu
Keyword(s):  
Experimental Data ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Centrifugal Pumps ◽  
Commercial Code ◽  
Calculation Results ◽  
Sst Turbulence Model ◽  
Specific Speed ◽  
Turbulent Models ◽  
Experimental Values

In order to research the applicability of turbulence model on characteristics prediction of centrifugal pumps at the design condition, standard k-ε turbulence model, k-ω turbulence model and SST turbulence model are selected, which are commonly used in the numerical prediction for head, efficiency and NPSHr of the centrifugal pumps. By using commercial code ANSYS CFX, the all three turbulent models are used to predict the characteristics of six centrifugal pumps with the different specific speeds at the design condition, which are varied from 34.3 to 260.5. The calculation results are compared with the experimental data, and the comparison indicates that all the prediction results obtained from different turbulence models are more or less different from the experimental data. The head and efficiency predicted by SST turbulence model and k-ω turbulence model are closer and they are all bigger than that predicted by k-ε turbulence model. For low specific speed centrifugal pumps, the head and efficiency predicted by SST model and the NPSHr predicted by k-ε turbulence model are more closer to the experimental values; while for the medium and high specific speed centrifugal pumps, the head and efficiency predicted by k-ε turbulence model are better than that predicted by other models. The k-ω turbulence model and k-ε turbulence model are the best choice to predict NPSHr of medium and high specific speed centrifugal pumps respectively.

Numerical Investigation on a High Endwall Angle Turbine With Swept-Curved Vanes

2018 ◽  
Author(s):  
Fusheng Meng ◽  
Jie Gao ◽  
Weiliang Fu ◽  
Xuezheng Liu ◽  
Qun Zheng
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Heat Load ◽  
Leading Edge ◽  
Field Calculation ◽  
Prediction Ability ◽  
Expansion Turbine ◽  
Sst Turbulence Model ◽  
Flow Loss ◽  
Lp Turbine

In a high endwall angle turbine, large meridional expansion can cause the strong secondary flow at the endwall, which results in a larger endwall flow loss than the small meridional expansion turbine. The endwall heat transfer is strongly affected by secondary flow effect. In order to optimize the endwall flow to reduce the flow loss and optimize the distribution of heat load, the swept-curved method was used in this study. The swept-curved method was investigated on a transonic second stator (S2) with large meridional expansion in a Low-Pressure (LP) Turbine. Validation studies were performed to investigate the aerodynamic and the heat transfer prediction ability of shear stress transport (SST) turbulence model. The influence of different shapes of the stacking line, including forward-swept, backward-swept, positive-curved and negative-curved, were investigated through numerical simulation. The parameterized control of swept-curved height and angle were adopted to optimize the performance of the aerodynamic and heat transfer. 3D flow field calculation captured the relatively accurate flow structures in the parts of endwall and near endwall. Heat transfer behaviors were explored by means of isothermal wall temperature and Nusselt number (Nu) distribution. The results show that the maximal heat transfer coefficient at the leading edge, for the formation of horseshoe vortexes that cause the high velocity towards the endwall. The swept vane can improve the static pressure and heat load distribution at the endwall region, which decreases the area-averaged shroud heat flux by 2.6 percent and the loss coefficient 1.3 percent.

Improving Flow Circulation in Heat Sinks Using Quadrupole Vortices

2009 ◽  
Author(s):  
Timothy J. Dake ◽  
Joseph Majdalani
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Leading Edge ◽  
Vortex Generators ◽  
Experimental Simulation ◽  
Second Phase ◽  
Performance Study ◽  
Planar Laser ◽  
Flow Circulation ◽  
Two Phases

In this paper, we show that improved air circulation above a heat sink is possible using thin winglet-type vortex generators that can be passively retrofitted to an existing unit. By mounting these vortex generators on the leading edge of heat sink fins, pairs of counter-rotating vortices are induced within the interfin spacing. The vortices disturb the boundary layers and serve to mix the air in the interfin channel. The devices we have designed are passive and can be added to existing systems using a simple clip-on mechanism. In this study, several designs are experimentally investigated for the purpose of identifying the optimal configuration that will be most conducive to flow enhancement and, therefore, heat transfer augmentation. Using the typical operational range of air velocities for PCs, routers and servers, an experimental simulation of the interfin channel reveals that certain vortex generators, when placed upstream, can outperform others in their ability to fill the channel with pairs of strong vortices. Multiple pairs can also be generated to further accentuate the heat transfer using dual vortex generators. A description of the specific shapes is furnished here along with particulars of the performance study. By control and manipulation of the vortices, our results suggest the possibility of optimizing the generator design. Experimentation was conducted in two phases. The first phase is a study of the ability to generate and control vortices within the fin channel. This aspect was simulated using a Lexan mock-up of the fin channel that permits introduction of glycerin smoke to visualize the shape, size, strength and structure of the vortices. The clear Lexan permitted viewing of the vortices by passing a red planar laser through the apparatus. The second phase involved using the optimization data gained in the first phase to generate vortices in an actual heat sink fitted with thermocouples to measure the temperatures at various points during heating.

scholarly journals An implicit scheme based on the LU-SGS method for URANS equations with SST turbulence model

2018 ◽  
pp. 1-20
Author(s):  
Vladislav Aleksandrovich Balashov ◽  
Vitaly Evgenyevich Borisov ◽  
Yana Vladislavovna Khankhasaeva
Keyword(s):  
Turbulence Model ◽  
Implicit Scheme ◽  
Sst Turbulence Model

A Combined CFD/MRV Study of Flow Through a Pin Bank

2014 ◽  
Author(s):  
Mike Siekman ◽  
David Helmer ◽  
Wontae Hwang ◽  
Gregory Laskowski ◽  
Ek Tsoon Tan ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Velocity Field ◽  
Turbulence Model ◽  
Field Data ◽  
Peak Velocity ◽  
Velocity Profiles ◽  
Mean Velocity ◽  
Magnetic Resonance Velocimetry ◽  
Sst Turbulence Model ◽  
Flow Through

RANS and time averaged URANS simulations of a pin bank are compared quantitatively and qualitatively to full 3D mean velocity field data obtained using magnetic resonance velocimetry (MRV). The ability of the CFD to match MRV velocity profiles through the pin bank is evaluated using the SST turbulence model. Quantitative comparisons of the velocity profiles showed an overprediction of peak velocity by the CFD at the first pin rows, and a smaller oscillatory error that diminishes as it moves through the pins, resulting in better matching towards the exit.

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