# 邊界層分離

## 逆压梯度

$u {\partial u \over \partial s} = -{1 \over \rho}{dp \over ds} + {\nu} {\partial^2 u \over \partial y^2}$

$dp/ds > 0$時，出現逆压梯度的現象，若逆压梯度夠大，會使得速度$u$沿著流線$s$減少，最後甚至可能變為零或負值[4]

## 影響邊界層分離的因素

$\rho u_o {du_o \over ds} = -{dp \over ds}$

${{\left. \frac{\text{d}u}{\text{d}s} \right|}_{y=0}}=0$ 并且 $\frac{{{\partial }^{2}}u}{\partial x\partial y}<0$

## 腳註

1. ^ Anderson, John D. (2004), Introduction to Flight, Section 4.20 (5th edition)
2. ^ Clancy, L.J., Aerodynamics, Section 4.14
3. ^ 3.0 3.1 Wilcox, David C. Basic Fluid Mechanics. 3rd ed. Mill Valley: DCW Industries, Inc., 2007. 664-668.
4. ^ Balmer, David. "Separation of Boundary Layers." School of Engineering and Electronics. 2 December 2007. University of Edinburgh. 12 March 2008 <http://www.see.ed.ac.uk/~johnc/teaching/fluidmechanics4/2003-04/fluids14/separation.html>
5. ^ Fielding, Suzanne. "Laminar Boundary Layer Separation." 27 October 2005. The University of Manchester. 12 March 2008 <http://www.maths.manchester.ac.uk/~suzanne/teaching/BLT/sec4c.pdf>.