A new turbulence closure model for boundary layer flows with strong adverse pressure gradients and separation

1984 ◽  
Author(s):  
D. JOHNSON ◽  
L. KING
Keyword(s):  
Boundary Layer ◽  
Turbulence Closure ◽  
Pressure Gradients ◽  
Closure Model ◽  
Boundary Layer Flows ◽  
Turbulence Closure Model

Measurements, Computation and Analysis of a Semi-Constrained, Axisymmetric Impinging Jet

2004 ◽  
Author(s):  
David A. Adolfson ◽  
Terrence W. Simon ◽  
Mounir B. Ibrahim
Keyword(s):  
Boundary Layer ◽  
Flow Visualization ◽  
Closed Form ◽  
Impinging Jet ◽  
Turbulence Closure ◽  
Transition To Turbulence ◽  
Closure Model ◽  
Form Analysis ◽  
Turbulence Closure Model ◽  
Closure Models

Experiments, closed-form analysis and computation were conducted to investigate flow in a semi-constrained, axisymmetric impinging jet. The aspect ratios (i.e. plate separation divided by jet diameter, S/D) were 0.25 and 0.59. Reynolds numbers based on jet diameter were approximately 7,600 and 17,700. Data collection was via hot-wire anemometry and flow visualization. Data consisted of a series of mean velocity profiles across the wall-jet boundary layer in the attached-flow region, power spectral distributions at selected points within the boundary layer and flow visualization. Spectra were used to help identify transition to turbulence of the wall layer. Flow visualization was conducted by seeding the flow with neutrally-buoyant bubbles, illuminating the bubbles with a laser sheet and capturing pictures with a standard 35mm camera. An approximate closed-form analysis is presented. It gives theoretical values of shear stress of a stagnation flow which approximately models the target plate flow and yields a set of parameters for generalizing the experimental and CFD results. Numerical simulations of the flow based upon solution of the RANS equations and various turbulence closure models are presented. Results of analyses with three different closure models are discussed in this paper: a) all laminar (no turbulence), b) k-ω turbulence closure model and c) k-ε turbulence closure model. The results from the k-ω model are generally in better agreement with the experimental results than are the k-ε model results. The performance of the three models is discussed. A need for proper modeling of transition within the flow is shown. This study serves to support computation of flows which have impingement, acceleration, adverse pressure gradients, transition to turbulence and flow separation using the low-aspect-ratio, semi-constrained, steady impinging jet.

Comparison of a Nonlinear k-ε Turbulence Closure Model With Stress Transport Models

1993 ◽  
Author(s):  
Muhammad A. R. Sharif ◽  
Yat-Kit E. Wong
Keyword(s):  
Pipe Flow ◽  
Flow Problem ◽  
Swirling Flow ◽  
Transport Model ◽  
Turbulent Pipe Flow ◽  
Turbulence Closure ◽  
Closure Model ◽  
Transport Models ◽  
Mean Velocity ◽  
Turbulence Closure Model

Abstract The performance of a nonlinear k-ϵ turbulence closure model (NKEM), in the prediction of isothermal incompressible turbulent flows, is compared with that of the stress transport models such as the differential Reynolds stress transport model (RSTM) and the algebraic stress transport model (ASTM). Fully developed turbulent pipe flow and confined turbulent swirling flow with a central non-swirling jet are numerically predicted using the Marker and Cell (MAC) finite difference method. Comparison of the prediction with the experiment show that all three models perform reasonably well for the pipe flow problem. For the swirling flow problem, the RSTM and ASTM is superior than the NKEM. RSTM and ASTM provide good agreement with measured mean velocity profiles. However, the turbulent stresses are over- or under-predicted. NKEM performs badly in prediction of mean velocity as well as the turbulent stresses.

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