BOUNDARY LAYER CONCEPT FOR EXTERNAL FLOW

KARTHIK.K 14BME069

MANOBALAA .R 14BME079

PALANISAMY.K 14BME094

PRADEEP.A 14BME100

DEEPAK ANANDH.M.B 14BME222

SRI PRASANTH.S 14BME227

BOUNDARY LAYER

A boundary layer is the layer of fluid in the

immediate vicinity of a bounding surface where

the effects of viscosity are significant.

SCOPE

Boundary layer traditionally includes the study of fluxes of heat, moisture and momentum between the atmosphere and the underlying surface, and how to characterize surfaces so as to predict these fluxes (roughness, thermal and moisture fluxes, radiative characteristics).

ASSUMPTIONS The boundary layer equations require several assumptions about the flow in the

boundary layer.

1. All of the viscous effects of the flow field are confined to the boundary layer,

adjacent to the wall .Outside of the boundary layer, viscous effects are not

important, so that flow can be determined by in viscid solutions such as potential

flow or Euler equations.

2. The viscous layer is thin compared to the wall.

3. The boundary conditions of the boundary layer region are the no-slip condition

at the wall, and the free-stream condition at infinity:

Hydrodynamic boundary layer

Boundary layer definitionBoundary layer thickness (d): defined as the distance away from the surface where the local velocity reaches to 99% of the free-stream velocity, that is u(y=d)=0.99U. Somewhat an easy to understand but arbitrary definition.Boundary layer is usually very thin: /x usually << 1.

BOUNDARY LAYER THICKNESS

δ(x) is the boundary layer thickness when u(y) =0.99V

V is the free-stream velocity The purpose of the boundary layer is to allow the fluid to change its velocity from the

upstream value of V to zero on the surface

EQUATIONS FOR 2D, LAMINAR, STEADY BOUNDARY LAYER FLOW

yT

yyTv

xTu

yu

ydxdUU

yuv

xuu

yv

xu

:energyofonConservati

:momentum-xofonConservati

0:massofonConservati

LITERATURE SURVEY- AN EXPERIMENTAL STUDY OF FILM COOLING IN ROTATING TURBINE Time-resolved measurements of heat transfer

on a fully cooled transonic turbine stage have been taken in a short duration turbine test facility which simulates full engine non-dimensional conditions. The time average of this data is compared to uncooled rotor data and cooled linear cascade measurements made on the same profile. The film cooling reduces the time-averaged heat transfer compared to the uncooled rotor on the blade suction surface by as much as 60%, but has relatively little effect on the pressure surface

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