Numerical Simulation of the Supersonic Inlet Flow Field

2010 ◽  
Vol 29-32 ◽  
pp. 2119-2123
Author(s):  
Da Min Cao ◽  
Hong Yang Lv ◽  
Xing Yuan Zhang ◽  
Sheng Bin Hu
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Static Pressure ◽  
Pressure Rise ◽  
Back Pressure ◽  
Supersonic Inlet ◽  
Simulation Results ◽  
Cfd Method

The 2-D internal steady flow of the scramjet inlet-isolator was numerically simulated by the CFD method. The static pressure contours of the scramjet inlet-isolator under different boundary thickness and different back pressure were given. The numerical simulation results of two kinds of reasons which make the inlet un-start are obtained. One is the boundary layer thickness and another is the high back pressure at the exit of the isolator. When the boundary layer thickness increased, air can not smoothly flow into the inlet isolator and caused inlet un-start. Sameness along with the back pressure rise, have the phenomenon of inlet un-start, too. But the reason of un-start is disaffiliate. In the text analyzed the reasons of un-start phenomenon which from two different perspectives on the problem.

Step-induced separation of a turbulent boundary layer in incompressible flow

1967 ◽  
Vol 27 (1) ◽  
pp. 111-130 ◽  
Author(s):  
P. Bradshaw ◽  
P. V. Galea
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Low Frequency ◽  
Pressure Rise ◽  
Initial Boundary ◽  
Simple Expression ◽  
Rapid Separation ◽  
Speed Flow ◽  
Extra Stress

Measurements of the low-speed flow up a step of height equal to 1·75 times the initial boundary-layer thickness show that the flow satisfies Stratford's (1959) condition for rapid separation, the extra stress gradients being confined to the first one-eighth of the boundary-layer thickness. The increase in turbulence intensity up to separation is small, and attributable to low-frequency fluctuations in separation position. Townsend's (1962) criterion predicts the separation point fairly accurately. A simple expression is found for the additional pressure rise that can be withstood by a boundary layer already fairly near separation, which gives tolerable results at any point in the flow up a step.

Some Boundary Layer Measurements on a Slender Wing at Supersonic Speeds

1963 ◽  
Vol 67 (629) ◽  
pp. 291-295
Author(s):  
R. T. Griffiths
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Aspect Ratio ◽  
Flat Plate ◽  
Layer Thickness ◽  
Incompressible Flow ◽  
Boundary Layer Thickness ◽  
Static Pressure ◽  
Leading Edge ◽  
Slender Wing

SummaryBoundary layer measurements have been made at four positions on a slender gothic wing of aspect ratio 0·75. Test's were made over a range of incidence at M=1·42 and 1·82. With transition fixed by roughness near the leading edge the boundary layer thickness varied little with small positive or negative incidence but was reduced at larger incidences, this being most marked at positive incidence for positions nearest the leading edge due to the influence of the wing vortex. With the exception of positions in the vicinity of the vortex, a good estimate of the boundary layer thickness was given by the theory for incompressible flow over a flat plate and an excellent estimate of the variation of local static pressure and Mach number with incidence was given by not-so-slender wing theory.

Numerical analysis of heat dissipation from a heated vertical cylinder by natural convection

2015 ◽  
Vol 231 (3) ◽  
pp. 405-413 ◽  
Author(s):  
Jashanpreet Singh ◽  
Chanpreet Singh
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Boundary Layer ◽  
Natural Convection ◽  
Layer Thickness ◽  
Water Vapour ◽  
Boundary Layer Thickness ◽  
Heat Dissipation ◽  
Convection Heat Transfer ◽  
Vertical Cylinder

Natural convection heat transfer from a hot vertical hollow brass cylinder has been studied experimentally and numerically. The governing equations of continuity, momentum and energy are discretised by using an implicit finite difference technique. The velocity and temperature profiles, boundary layer thickness, local and average heat transfer coefficient are obtained using the numerical simulation. The predictions of the numerical simulation are compared with the experiments conducted on a laboratory-scale apparatus and with the results obtained from analytical solutions available in literature. The numerical simulation results are obtained for two fluids; air and water vapour whereas the experiments are conducted for air only. The induced flow is laminar in both the simulation and the experiments. The dependence of boundary layer thickness on Prandtl number is discussed. The numerically obtained Nusselt number is found quite close to the analytical one. The results show the heat dissipation from the cylinder to surrounding fluid is higher for air than for water vapour. The various factors that affect the comparison of the experimental results with the numerical simulation are discussed.

Numerical Investigation of Dump Diffuser Combustor Performance at Uniform and Non-Uniform Inlet Conditions

2020 ◽  
Author(s):  
Heyu Wang ◽  
Kai Hong Luo
Keyword(s):  
Boundary Layer ◽  
Numerical Investigation ◽  
Layer Thickness ◽  
Pressure Loss ◽  
Total Pressure ◽  
Boundary Layer Thickness ◽  
Static Pressure ◽  
Aerodynamic Performance ◽  
Aero Engine ◽  
Inlet Conditions

Abstract A numerical investigation has been conducted for an axisymmetric dump diffuser combustor, which is a simplified geometry of a typical lean-burn combustor in a modern civil aero-engine gas turbine. The aerodynamic performance of the combustor is analyzed with an emphasis on two common performance parameters: static pressure recovery and total pressure loss. The former is essential in maintaining high-pressure air flow across the liner, whereas the latter involves the specific fuel consumption of the aero-engine. At first, the effects of geometrical parameters of the dump diffuser combustor are investigated. A high diffuser angle seems to be detrimental to both static pressure recovery and total pressure loss. On the other hand, a high dump gap ratio is beneficial from the aerodynamic performance point of view. However, all these desired characteristics are subject to mechanical constraints and their implications for specific consumption. Optimum values of those parameters should exist for a given desired aerodynamics performance. The majority of previous researches, including the first part of this study, have been carried out with uniform inlet conditions due to a typical independent design cycle of each component. The effects of compressor exit conditions are usually not considered in the early stage design process. In the second part of this study, various inlet conditions representing a more realistic compressor exit condition such as inlet symmetrical and asymmetrical boundary layer thickness are investigated. The performance of an asymmetrical configuration with a thin boundary layer thickness near the outer annulus is almost comparable to that of its uniform counterpart. Findings of this study provide useful input for combustor designers to improve the combustor’s performance based on the compressor exit conditions.

Study on the Effects of Upstream Flow Conditions and Clearance Sizes to Tip Leakage Flow in a Subsonic Large-Scale Rotor

2014 ◽  
Author(s):  
Chenkai Zhang ◽  
Jun Hu ◽  
Zhiqiang Wang ◽  
Ning Ding ◽  
Zhiming Mao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Operating Condition ◽  
Tip Leakage

To clearly clarify how it affects the detailed tip clearance flow and flow mechanism by varying the upstream boundary layer thickness and tip clearance size, numerical studies were performed on a subsonic rotor, which is used for low-speed model testing of one rear stage embedded in a modern high-pressure compressor. Firstly, available experimental data were adopted to validate the numerical method. Second, comparisons were made for tip leakage vortex structure, the interface of leakage flow/mainflow, endwall loss, isentropic efficiency and pressure-rise between different operating conditions. Then, effects of different clearance sizes and inlet boundary layer thicknesses were investigated. At last, the self-induced unsteadiness at one near-stall operating condition was studied for different cases. Results show that increasing the tip clearance size has a deleterious effect on rotor efficiency and pressure-rise performance over the whole operating range, while thickening the inflow boundary layer is almost the same except that its pressure-rise performance will be increased at mass flow rate larger than design operating condition. Self-induced unsteadiness occurs at near-stall operating conditions, and its appearance depends largely on tip clearance size, while upstream boundary layer thickness has little effect.

scholarly journals Numerical Simulation of Low-Permeability Reservoirs with considering the Dynamic Boundary Layer Effect

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Chuanzhi Cui ◽  
Yingfei Sui ◽  
Xiangzhi Cheng ◽  
Yinzhu Ye ◽  
Zhen Wang
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Porous Medium ◽  
Pressure Gradient ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Low Permeability ◽  
Boundary Layer Effect ◽  
Layer Effect ◽  
Low Permeability Reservoirs

Surface active components, salt component, and polar molecules in the fluid may adsorb on the solid surface and form the boundary layer during low-speed flow in a porous medium, which will influence the flowing law in the porous medium. Previous studies on flowing in low-permeability reservoirs mainly focus on the effects of the threshold pressure gradient. But few of them have considered the time-varying effect of the boundary layer thickness in solving the numerical simulation. The correlation among the boundary layer thickness and pressure gradient was established by regressing the experimental data of boundary thickness versus pressure. On this basis, the mathematical model of oil-water two-phase flow which involves influence of the boundary layer was constructed, and the comparative analysis of the development effect is performed. Results demonstrated that the boundary layer thickness is sensitive to the throat radius and pressure gradient, and the boundary layer thickness decreases dynamically with the increase of pressure gradient. The displacement velocity and accumulative oil production with boundary layer effect decrease when comparing with that without the boundary layer effect. Meanwhile, the boundary layer accelerates the breakthrough of water. With the reduction of production pressure difference, the difference between accumulative oil production with and without the boundary layer effect increases, which indicate that the dynamic effect of the boundary layer is intensified.

The Influence of Tabs on Different Area Ratio Short Annular Diffusers

2014 ◽  
Author(s):  
D. J. Cerantola ◽  
A. M. Birk
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Pressure Coefficient ◽  
Area Ratio ◽  
Back Pressure ◽  
Swirl Number ◽  
Inlet Flow ◽  
Flow Blockage

Square tabs were placed on the base of an ellipsoidal centre body in annular diffusers with length to inlet height of 12. Tests were completed with an inlet Reynolds number of 1 × 105, swirl number of 0.71, and inlet flow blockage of 0.02–0.04. Four outer walls were manufactured with area ratios of 1.61, 1.91, 2.73, and 6.18. The tabs with a projected height equivalent to the boundary layer thickness were effective at reducing the outlet distortion but at a pressure penalty for the three smaller diffusers. The largest diffuser improved back pressure coefficient 4.6% with four tabs providing a blockage of 4.7% over its bare diffuser but was 42% lower than that obtained by the AR = 2.73 diffuser with no tabs.

Investigations on the Effects of Inflow Condition and Tip Clearance Size to the Performance of a Compressor Rotor

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Chenkai Zhang ◽  
Jun Hu ◽  
Zhiqiang Wang
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Operating Condition ◽  
Compressor Rotor ◽  
High Pressure Compressor ◽  
Inflow Condition

To clearly clarify the effects of different upstream boundary layer thickness and tip clearance size to the detailed tip flow field and flow mechanism, numerical simulations are performed on a subsonic compressor rotor, which is used for low-speed model testing of a rear stage embedded in a modern high-pressure compressor. First, available experimental data are adopted to validate the numerical method. Second, comparisons are made for tip leakage vortex (TLV) structure, the interface of leakage flow/mainflow, endwall loss, isentropic efficiency and pressure-rise among different operating conditions. Then, effects of different clearance sizes and inflow boundary layer thicknesses are investigated. Finally, the self-induced unsteadiness at one near-stall (NS) operating condition is studied for different cases. Results show that the increment of tip clearance size has a deleterious effect on rotor efficiency and pressure-rise performance over the whole operating range, while thickening the inflow boundary layer is almost the same except that its pressure-rise performance will be increased at mass flow rate larger than design operating condition. Self-induced unsteadiness occurs at NS operating conditions, and its appearance largely depends on tip clearance size, while the effect of upstream boundary layer thickness is little.

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