Wall pressure and shear stress measurements beneath an impinging jet

Deformation and dewetting of thin liquid films induced by moving gas jets

“…This critical Reynolds number scales as Re D,min $ Ca 0.52 for h min = 500 nm with a slightly increasing exponent for lower h min . Since the jet pressure distribution P jet decays much faster [37][38][39][40]13] with distance from the nozzle than the shear stress distribution s jet , the two relevant components of Q y at the front rim are s y h 2 /(2l) and U sub h. From a balance of these terms and the approximate scaling s $ Re 2 D [13], the critical Reynolds number required to reach a certain minimum film thickness scales with ffiffiffiffiffiffiffiffiffi U sub p or Ca 0.5 in excellent agreement with Fig. 5a.…”

“…In the axisymmetric case [44,37], the wall shear stress at large distances from the impingement point scales as s jet -$ r À11/4 , whereas the stagnation pressure distribution P jet (r) decays rapidly [39,13] for distances exceeding D. We first consider the steady state height profile along the jet trajectory, i.e. the y-axis in our rectilinear model, corresponding to the profiles in Fig.…”

Numerical Modeling of a Planar Unconfined Oblique Jet Moving Along the Ground Surface

“…For the current study a validation of jet impingement is also important. Tu and Wood (1996) presented experimental data for pressure coefficient and wall shear stress of a normal impinging jet at Reynolds number of 11,000 and ground distances r/D=4, 12. The experimental data is compared with numerical simulations in Fig.…”

“…Impinging jets are often utilized to enhance heat transfer and mixing in the impingement region. Common applications that take advantage of these enhancements include jets used for heating, cooling, drying of materials (Shi, Ray and Mujumdar, 2003), film and coating thickness control (Tu and Wood, 1996), aerodynamic support (Gallington, 1987), and production of air curtains (Beaubert and Viazzo, 2003). Although the focus of the current study is on supporting jet aerodynamics, the results are useful for many other applications.…”

“…For practical applications the jet source must be placed sufficiently high to avoid collisions with obstacles or contacts with water waves. Similar to the V/STOL craft, a ground vortex may also cause hot gas or contaminant ingestion which hampers the performance of jet propulsors (Tafti and Vanka, 1991 Tu and Wood (1996). In the experiments of Krothapalli (1987) cross flow was introduced as the jet exited normally from the bottom of an NACA 0018 wing section and impinged on the ground.…”