In

all turbulent flows velocity fields fluctuate rapidly both in space and time. Computationally

it is very expensive to directly simulate both the small scale and high

frequency fluctuations for any useful engineering problem. There are two

methods to eliminate the need to resolve these small scales and high

frequencies namely, Reynolds Averaging and Filtering. For this paper, we are

only concerned with the Reynolds Averaging. In this method all flow variables

are divided into a mean component and a rapidly fluctuating component and then

all equations are time averaged to remove the rapidly fluctuating components.

For the continuity equation the new equation is identical to the original

equation, except that the transported variables now represent the mean flow

quantities. In the Navier-Stokes equation however new terms appear which

involve mean values of products of rapidly varying quantities. These new terms

are known as the Reynolds Stresses, and solution of the Reynolds Averaged

Navier-Stokes (RANS) equation initially involves the construction of suitable models

to represent these Reynolds Stresses. These models include various one equation

and two equation models, like Spalart Allmaras,

K-omega, K-epsilon etc.

A

low Reynolds number one equation Spalart-Allmaras turbulence model has been

selected for numerically simulating the junction flow with localized suction in

order to study the RANS capability for prediction of such flows. This has been

selected due to its known ability of the turbulence model to predict the flow

within the boundary layer right down into the laminar sub-layer. This

turbulence model is widely used for predictions of wall-bounded flows and it is

believed to perform well for boundary layers subjected to adverse pressure

gradients 9. This aspect of the turbulence model should be important in the

planned three dimensional half wing application, since this involves junction

flow separation which originates due to the adverse pressure gradient effects

upstream of the wing leading edge.