Griffith Diffusers

1979 ◽  
Vol 101 (4) ◽  
pp. 473-477 ◽  
Author(s):  
Tah-teh Yang ◽  
C. D. Nelson
Keyword(s):  
Boundary Layer ◽  
Inverse Method ◽  
Area Ratio ◽  
Two Dimensional ◽  
High Lift ◽  
Boundary Layer Suction ◽  
Through Flow ◽  
Typical Performance ◽  
Method Of Solution ◽  
Layer Control

Contoured wall diffusers are designed by using an inverse method. The prescribed wall velocity distribution(s) was taken from the high lift airfoil designed by A. A. Griffith in 1938; therefore, such diffusers are named Griffith diffusers. First the formulation of the inverse problem and the method of solution are outlined. Then the typical contour of a two-dimensional diffuser and velocity distributions across the flow channel at various stations are presented. For a Griffith diffuser to operate as it is designed, boundary layer suction is necessary. Discussion of the percentage of through-flow required to be removed for the purpose of boundary layer control is given. The typical performance is presented for a Griffith diffuser having the ratio (Cpmeasured / Cpideal) = 98 percent and at the exit plane the ratio of (Ulocal − Uavg.) / Uavg. = ± 5 percent. Finally, reference is made to the latest version of a computer program for a two-dimensional diffuser requiring only area ratio, nondimensional length and suction percentage as inputs.

Comparative study of boundary layer control around an ordinary airfoil and a high lift airfoil with secondary blowing

2018 ◽  
Vol 164 ◽  
pp. 50-63 ◽  
Author(s):  
Sandeep Eldho James ◽  
Abhilash Suryan ◽  
Jiss J Sebastian ◽  
Abhay Mohan ◽  
Heuy Dong Kim
Keyword(s):  
Boundary Layer ◽  
Comparative Study ◽  
Boundary Layer Control ◽  
High Lift ◽  
Layer Control

Some Measurements of Boundary-Layer Growth in a Two-Dimensional Diffuser

1959 ◽  
Vol 81 (3) ◽  
pp. 285-294 ◽  
Author(s):  
J. F. Norbury
Keyword(s):  
Boundary Layer ◽  
Static Pressure ◽  
Momentum Equation ◽  
Layer Growth ◽  
Area Ratio ◽  
Momentum Thickness ◽  
Two Dimensional ◽  
Static Pressure Distribution ◽  
Boundary Layer Growth ◽  
Flow Experiments

Low-speed experiments were carried out in a two-dimensional diffuser having a square throat and an area ratio of two to one. Measurements were made of static pressure distribution, velocity contours at throat and outlet, and boundary-layer growth along the four wall center lines. Visual flow experiments were performed using tufts and smoke filaments. Similar experiments were carried out with the throat boundary layers artificially thickened by means of round rods placed on the walls upstream. Disparities between the measured growth of momentum thickness and that predicted by the simple momentum equation are discussed, as well as the effect of the artificial thickening on diffuser efficiency.

Boundary-Layer Control as a Means of Reducing Drag on Fully Submerged Bodies of Revolution

1985 ◽  
Vol 107 (3) ◽  
pp. 342-347 ◽  
Author(s):  
B. Bar-Haim ◽  
D. Weihs
Keyword(s):  
Boundary Layer ◽  
Reynolds Numbers ◽  
Boundary Layer Transition ◽  
Boundary Layer Control ◽  
Layer Transition ◽  
Bodies Of Revolution ◽  
Boundary Layer Suction ◽  
Technique Optimization ◽  
Axisymmetric Bodies ◽  
Layer Control

The drag of axisymmetric bodies can be reduced by boundary-layer suction, which delays transition and can control separation. In this study, boundary-layer transition is delayed by applying a distributed suction technique. Optimization calculations were performed to define the minimal drag bodies at Reynolds numbers of 107 and 108. The saving in drag relative to optimal bodies with non-controlled boundary layers is shown to be 18 and 78 percent, at Reynolds numbers of 107 and 108, respectively.

scholarly journals Modeling of Turbulent Fluid Flow Over a Rough Wall With or Without Suction

2003 ◽  
Vol 125 (4) ◽  
pp. 636-642 ◽  
Author(s):  
G. Gre´goire ◽  
M. Favre-Marinet ◽  
F. Julien Saint Amand
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Fluid Flow ◽  
Rough Boundary ◽  
Two Dimensional ◽  
Turbulent Fluid Flow ◽  
Boundary Layer Suction ◽  
Zonal Model ◽  
Impermeable Wall ◽  
Logarithmic Law

The turbulent flow close to a wall with two-dimensional roughness is computed with a two-layer zonal model. For an impermeable wall, the classical logarithmic law compares well with the numerical results if the location of the fictitious wall modeling the surface is considered at the top of the rough boundary. The model developed by Wilcox for smooth walls is modified to account for the surface roughness and gives satisfactory results, especially for the friction coefficient, for the case of boundary layer suction.

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