Pipe flow

About: Pipe flow is a research topic. Over the lifetime, 13826 publications have been published within this topic receiving 351605 citations.

Transonic Shocks in Compressible Flow Passing a Duct for Three-Dimensional Euler Systems

Abstract: In this paper we study the transonic shock in steady compressible flow passing a duct. The flow is a given supersonic one at the entrance of the duct and becomes subsonic across a shock front, which passes through a given point on the wall of the duct. The flow is governed by the three-dimensional steady full Euler system, which is purely hyperbolic ahead of the shock and is of elliptic–hyperbolic composed type behind the shock. The upstream flow is a uniform supersonic one with the addition of a three-dimensional perturbation, while the pressure of the downstream flow at the exit of the duct is assigned apart from a constant difference. The problem of determining the transonic shock and the flow behind the shock is reduced to a free-boundary value problem. In order to solve the free-boundary problem of the elliptic–hyperbolic system one crucial point is to decompose the whole system to a canonical form, in which the elliptic part and the hyperbolic part are separated at the level of the principal part. Due to the complexity of the characteristic varieties for the three-dimensional Euler system the calculus of symbols is employed to complete the decomposition. The new ingredient of our analysis also contains the process of determining the shock front governed by a pair of partial differential equations, which are coupled with the three-dimensional Euler system.

Applying hypothesis of self-similarity for flow-resistance law of small-diameter plastic pipes

Abstract: In this paper the writer reports the results of an investigation carried out to test the applicability of the self-similarity hypothesis for determining the flow-resistance law in small-diameter plastic pipes. The incomplete self-similarity (ISS) hypothesis is applied for establishing both the flow-resistance law and the velocity distribution. The analysis shows that the head loss per unit length can be accurately estimated using a theoretical approach based on the ISS hypothesis for the velocity profile in a circular smooth pipe. A new relationship between the Γ coefficient of the power-velocity profile and the flow Reynolds number, based on previous measurements carried out in plastic polyethylene (PE) pipes with nominal diameter equal to 16, 20, and 25 mm and for flow Reynolds numbers ranging from 3,037 to 36,112, is also established.

Mixing and flow regulating by induced-charge electrokinetic flow in a microchannel with a pair of conducting triangle hurdles

Abstract: The induced-charge electrokinetic flow (ICEKF) in a rectangular micorchannel with a pair of conducting triangle hurdles embedded in the middle is investigated in this paper. A correction method is suggested to numerically estimate the induced zeta potential on the conducting surface. Two-dimensional pressure-linked Navier-–Stokes equation is used to model the flow field in the channel. The numerical results show flow circulations generated from the induced non-uniform zeta potential distribution along the conducting hurdle surfaces. It is demonstrated numerically that the local flow circulations provide effective means to enhance the flow mixing between different solutions; by adjusting the electric field applied through the microchannel with a non-symmetric triangle hurdle pair, an electrokinetic flow regulating effect can be obtained and this effect depends on the dimensions of the conducting converging–diverging section. The mixing and flow regulating using ICEKF described in this paper can be used in various microfluidics and lab-on-a-chip (LOC) applications.