Flows in natural fluid layers are often forced simultaneously at scales smaller and much larger than the depth. For example, the Earth’s atmospheric flows are powered by gradients of solar heating: vertical gradients cause three-dimensional (3D) convection whereas horizontal gradients drive planetary scale flows. Nonlinear interactions spread energy over scales1,2. The question is whether inter...

and the Problem of Turbulence in the Age of Supercomputers Morteza Gharib Professor of Aeronautics, Center for Quantitative Visualization, Graduate Aeronautical Laboratories, Pasadena, CA 91125 Due to the rising capabilities of computational fluid mechanics ( CFD), the role of the experimentalist in solving the problem of turbulence has come under serious question. However, after much initial e...

The multiscale method for computational fluid dynamics (CFD) is proposed to solve viscous flow problems at high Reynolds numbers with a thin boundary layer. This method is a physics-based model, uses generalized hydrodynamic equations proposed by Alexeev (1994), and can be interpreted as a regularization of the Navier-Stokes equations. Numerical solutions using this approach compare favorably w...

A new universal theory for flow instability and turbulent transition is proposed in this study. Flow instability and turbulence transition have been challenging subjects for fluid dynamics for a century. The critical condition of turbulent transition from theory and experiments differs largely from each other for Poiseuille flows. This enigma has not been clarified so far owing to the difficult...

One of the important properties of boundary layer is, from the point of view of Strömungslehre, that it pumps vorticity into the flow field. Vorticity in fluid flows plays diverse roles and produces tremendous variety of flow phenomena. We consider four aspects of vorticity in fluid flows: (A) Kinematical aspect of a vortex sheet, (B) mechanical aspect of hydrodynamic impulse of a vortex system...

A computationally efficient method to approximate the total sound power and far-field acoustic intensity spectra generated by turbulent flow past a rigid body is proposed. The method is based on Proudman’s analytical formula for the sound generated by isotropic turbulence. This formula expresses the sound intensity of locally isotropic turbulence for low Mach numbers in terms of the kinetic ene...

a large eddy, or vortex, that spins within the sinus cavity. The fluid motion within similar recirculating flows is known to be unstable with an early transition to turbulence. The stability of the aortic sinus vortex was examined in the current study in an in vitro pulsatile flow rig. The geometry of the experimental test section was the same as the geometry of the natural aortic root. Differe...

The dual cascade of enstrophy and energy in quasi-two-dimensional turbulence strongly suggests that a viscous but otherwise potential vorticity (PV) conserving system decays selectively toward a state of minimum potential enstrophy. We derive a nonperturbative mean field theory for the dynamics of minimum enstrophy relaxation by constructing an expression for PV flux during the relaxation proce...

─ Supersonic flows associated with missiles, aircraft, missile engine intake and rocket nozzles are often steady. The shape of the nozzle geometry is increasingly attractive in heating, ventilation and air conditioning applications. The objective of the present work is to simulate and understand Supersonic flows with twin free jet Flow at various Mach numbers. The purpose is to precisely unders...