ESDU 00006
Drag of rectangular planform cavity in a flat plate with a turbulent boundary layer for Mach numbers up to 3. Part I: Closed flow
Abstract:
ESDU 00006 develops a method for predicting the drag where the cavity length is large compared to the depth and the shear flow enters the cavity and attaches to the floor before separating to pass over the rear wall with a stagnation point near the top of the wall (i.e. closed flow). A family of curves suggests an upper limit of cavity depth to length ratio for closed flow in terms of freestream Mach number and cavity width to length or width to height ratio. In supersonic flow it is possible for vortices to form as the shear flow spills over the side edges of the cavity and their impingement on the rear wall gives rise to an increase in drag for which an estimation method is also provided.
Tables give the ranges of parameters covered in the construction of the method. The prediction of the ratio of the drag coefficient, based on floor area, to the local skin friction coefficient at the cavity midlength station (in the absence of the cavity) is assessed to be within 1 for lowspeed flow (Mach number less than 0.1) and to within 2 for highspeed flow (Mach number between 0.5 and 3). Worked examples illustrate the use of the method. A companion ESDU document, ESDU 00007, deals with other types of cavity flow, known as transitional and open. The third Item in the series, ESDU 10016, deals with the effect on cavity drag of a pair of doors open at 90°, including the effects of three different treatments of the door leading and trailing edges.
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Data Item ESDU 00006  

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This Data Item contains 15 interactive graph(s) as listed below.
Graph  Title 

Figure 1  Boundaries for closed flow (closed flow likely below each curve) 
Figure 2  Cavity width factor, F 
Figure 3  Value of a_{0} 
Figure 4  Cavity width factor, G 
Figure 5  Value of b_{0} 
Figure 6  Mach number factor on a_{0} 
Figure 7  Mach number factor on b_{0} 
Figure 8  Mach number factor on a_{rw0} 
Figure 9  Mach number factor on b_{rw0} 
Figure 10  Factor on C_{Drw}/C_{fm} to give drag due to sideedge vortices 
Figure 11  Exponent in Equation (4.25) for C_{fm} 
Figure 12  Mach number factors for C_{fm} 
Figure 13  Local skin friction coefficient on a flat plate 
Figure 14  Boundary layer thickness on a flat plate 