We demonstrate a close analogy between a viscoelastic medium and an electrically conducting fluid containing a magnetic field. Specifically, the dynamics of the Oldroyd-B fluid in the limit of large Deborah number corresponds to that of a magnetohydrodynamic (MHD) fluid in the limit of large magnetic Reynolds number. As a definite example of this analogy, we compare the stability properties of ...

Abstract. We carry out direct numerical simulation (DNS) of turbulent flow in pipes with a grit-blasted surface, to investigate both on momentum and heat transfer. A wide range Reynolds numbers are considered, while maintaining constant molecular Prandtl number 0.7. The large relative roughness influences the velocity temperature fields, indicating that analogy does not hold at high bulk number.

In the fully rough regime, proposed models predict a scaling for roughness heat-transfer coefficient, e.g. Stanton number ${St}_k \sim (k^+)^{-p} {Pr}^{-m}$ where exponent values $p$ and $m$ are model dependent, giving diverse predictions. Here, $k^+$ is Reynolds ${Pr}$ Prandtl number. To clarify this ambiguity, we conduct direct numerical simulations of forced convection over three-dimensional...

Although the Lighthill–Curle acoustic analogy theory is formally exact, presence of linear source terms related to viscous stresses and non-isentropic density changes makes it unsuitable for studying aerodynamic sound generation in low Reynolds number thermoviscous flows. Here we use an extension Ffowcs Williams Hawkings formulation, with effects explicitly included, find analytical solution ca...

In the last few decades a series of experiments have revealed that turbulence is a cooperative and critical phenomenon showing a continuous phase change with the critical Reynolds number at its onset. However, the applications of phase transition models, such as the Mean Field Theory (MFT), the Heisenberg model, the XY model, etc. to turbulence, have not been realized so far. Now, in this artic...

Dynamical processes in granular media show fascinating behavior @1–4#. The particular role of disorder and fluctuations in granular dynamics has led several authors @1,5–7# to propose an analogy to frustrated statistical systems such as spin glasses @8#. Recently a frustrated lattice gas model has been introduced to describe static and dynamic properties of granular materials @9#. This microsco...

Transitional flow, whereby the motion of a fluid changes from laminar to turbulent flow, was successfully identified by Reynolds (1883) almost 130 years ago. According to ASHRAE (2009), for a round pipe, in general, laminar flow exists when the Reynolds number is less than 2 300. Fully turbulent flow exists when the Reynolds number is larger than 10 000 and transitional flow exists for Reynolds...

Jets are one of the most fascinating topics in fluid mechanics. For aeronautics, turbulent jet-noise modelling is particularly challenging, not only because of the poor understanding of high Reynolds number turbulence, but also because of the extremely low acoustic efficiency of high-speed jets. Turbulent jet-noise models starting from the classical Lighthill acoustic analogy to state-of-the ar...

We address the experimentally observed non-Gaussian fluctuations for the energy injected into a closed turbulent flow at fixed Reynolds number. We propose that the power fluctuations mirror the internal kinetic energy fluctuations. Using a stochastic cascade model, we construct the excess kinetic energy as the sum over the energy transfers at different levels of the cascade. We find an asymmetr...

This paper presents experimental studies of aero-optical distortions due to a turbulent boundary layer over a range of subsonic speeds with the underlying wall both heated above and cooled below the adiabatic wall temperature. A statistical scaling model, based on Extended Strong Reynolds Analogy is derived and shown to correctly predict experimentally-observed results. The temperature mismatch...