Reducing wall drag in turbulent pipe and channel flows is an issue of great practical importance. In engineering applications, end-functionalized polymer chains are often employed as agents to reduce drag. These polymers which floating the solvent attach (either by adsorption or through irreversible chemical binding) at one their chain ends substrate (wall). We propose a PDE model study this se...

We did an experimental study on Taylor-Couette flow in between two coaxial cylinders of length L = 220 mm and radii r i = 110 and r o = 120, respectively, the fluid-filled 'Taylor-Couette gap' or TC-gap being h = 10 mm, thus gap ratio η = r i /r o = 0.917, and gap aspect ratio L/h = 22). Both cylinders are rotating independently, with angular frequencies ω i,o , The torque T on the inner cylind...

Based on shear strength reduction finite element method, stability of retaining wall with relieving plate has been analyzed. Due to the structure character of retaining wall with relieving plate, it can be found that fracture surface could hardly cross the triangle area of between lower wall and soleplate, between upper wall and relieving plate, so the second fractured surface occurred at there...

boundary-layeredge is still slightly freestreamdependent, the level of eddy viscosity and therefore also the skin-friction coefŽ cient are not. Furthermore, the velocity distribution is consistent with the law-of-the-wall solution. As a second test case, the RAE2822 airfoil is considered (in particular, case 9 of Ref. 11). Figure 2 compares the pressure and skinfriction distributions of the dif...

We compute the wall velocity in the MSSM with W , tops and stops contributing to the friction. In a wide range of parameters including those which fulfil the requirements of baryogenesis we find a wall velocity of order vw ≈ 10 −2 much below the SM value. 1 Bubble Wall Equation of Motion in the MSSM Energy conservation leads to the equations of motion of an electroweak bubble wall interacting w...

In contrast to most fluids, flowing powders do not exhibit viscosity such that a Newtonian rheology cannot accurately describe granular flow. Assuming that the material is incompressible, dry, cohesionless, and perfectly rigid-plastic, generalized Navier-Stokes equations (’Schaeffer Model’) have been derived where the velocity gradient has been replaced by the shear rate, and the viscosity depe...

The scaling of the kinematic boundary layer thickness λu and the friction factor Cf at the topand bottom-wall of Rayleigh-Bénard convection is studied by Direct Numerical Simulation (DNS). By a detailed analysis of the friction factor, a new parameterisation for Cf and λu is proposed. The simulations were made of an L/H = 4 aspect-ratio domain with periodic lateral boundary conditions at Ra = {...

Mechanical energydissipation is important forvibrationdampingandsoundabsorption. Thispaperprovides an analytical model for the interfacial-friction-based viscous behavior of exfoliated graphite, thereby establishing a methodology that may be applied to such behavior of materials in general. This model is in contrast to the conventional bulk viscous deformation model. It can be used to predict t...

We report large-eddy simulation (LES) of turbulent channel flow. This LES neither resolves nor partially resolves the near-wall region. Instead, we develop a special near-wall subgrid-scale (SGS) model based on wall-parallel filtering and wall-normal averaging of the streamwise momentum equation, with an assumption of local inner scaling used to reduce the unsteady term. This gives an ordinary ...

In this thesis, unsteady friction in transient pipe flow is given a closer look. The common quasi-steady friction model and two one-dimensional convolution-based models, developed by Zarzycki and Vardy & Brown, are considered. A quasi-two-dimensional approach to the water hammer problem is also derived, where the pipe friction is related to the near-wall behavior of the velocity profile. The mo...