Shape of the subsonic part of a nozzle with a flat acoustic surface with allowance for viscosity in the boundary-layer approximation

1982 ◽  
Vol 42 (5) ◽  
pp. 491-495
Author(s):  
I. L. Osipov ◽  
A. V. Shipilin ◽  
N. P. Shulishnina

It is shown that the boundary layer approximation to the flow of a viscous fluid past a flat plate of length l , generally valid near the plate when the Reynolds number Re is large, fails within a distance O( lRe -3/4 ) of the trailing edge. The appropriate governing equations in this neighbourhood are the full Navier- Stokes equations. On the basis of Imai (1966) these equations are linearized with respect to a uniform shear and are then completely solved by means of a Wiener-Hopf integral equation. The solution so obtained joins smoothly on to that of the boundary layer for a flat plate upstream of the trailing edge and for a wake downstream of the trailing edge. The contribution to the drag coefficient is found to be O ( Re -3/4 ) and the multiplicative constant is explicitly worked out for the linearized equations.


1960 ◽  
Vol 27 (4) ◽  
pp. 749-750
Author(s):  
G. Horvay

A simple boundary-layer approximation formula is derived for the temperature distribution in liquid metal which flows past a porous flat plate at zero incidence at velocity U and is sucked into it at velocity V.


Author(s):  
Takashi Takata ◽  
Akira Yamaguchi ◽  
Masaaki Tanaka ◽  
Hiroyuki Ohshima

Turbulent statistics near a structural surface, such as a magnitude of temperature fluctuation and its frequency characteristic, play an important role in damage progression due to thermal stress. A Large Eddy Simulation (LES) has an advantage to obtain the turbulent statistics especially in terms of the frequency characteristic. However, it still needs a great number of computational cells near a wall. In the present paper, a two-layer approach based on boundary layer approximation is extended to an energy equation so that a low computational cost is achieved even in a large-scale LES analysis to obtain the near wall turbulent statistics. The numerical examinations are carried out based on a plane channel flow with constant heat generation. The friction Reynolds numbers (Reτ) of 395 and 10,000 are investigated, while the Prandtl number (Pr) is set to 0.71 in each analysis. It is demonstrated that the present method is cost-effective for a large-scale LES analysis.


1982 ◽  
Vol 117 ◽  
pp. 211-231 ◽  
Author(s):  
Mostafa A. Foda

An analytical theory is developed to describe how negative pressure, (or ‘mud suction’, as it is sometimes referred to) develops underneath a body as it detaches itself from the ocean bottom. Biot's quasistatic equations of poro-elasticity are used to model the ocean bottom, and a general three-dimensional time-dependent analysis of the problem is worked out first using the boundary-layer approximation recently proposed by Mei and Foda. Then, explicit leading-order analytical solutions are presented for the problems of extrication of slender bodies as well as axisymmetric bodies from the ocean bottom.


2015 ◽  
Author(s):  
Helio Ricardo de Aguiar Quintanilha Júnior ◽  
Leonardo Santos de Brito Alves ◽  
Oberdan Miguel Rodrigues de Souza ◽  
Marcio Teixeira de Mendonça

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