in this study, a numerical computational fluid dynamics study is conducted in order to predict the aerodynamic forces on the np car. the turbulent air flow around the car is modeled using the realizable k-ε model. first, results are validated against those presented for the ahmed’s body. next, the fluid flow around the car is simulated for different car speeds ( to mph) and flow directions ( to...

Many existing phenomena in nature are considered new design ideas in various fields of industry. Bionics is the application of biological methods and systems found in nature to the study and design of engineering systems and modern technology. By performing bionic review, the researchers found the penguins by delivering air locked under their wings and creating air bubbles, the drag significant...

this paper presents efflux time experiments performed in the absence and presence of aqueous solutions of drag reducing agents (dras) when a liquid is emptied from a large open cylindrical storage tank through an exit piping system. the drag reducing agents studied are dodecyl benzene sulfonate anionic surfactant and a mixed solution of surfactant and sodium chloride counter ion. the variables ...

The objective of this paper is to examine the effectiveness of wall oscillation as a control scheme of drag reduction. Two flow configurations are considered: constant flow rate and constant mean pressure gradient. The Navier-Stokes equations are solved using Fourier-Chebyshev spectral methods and the oscillation in sinusoidal form is enforced on the walls through boundary conditions for the sp...

In this study, a numerical computational fluid dynamics study is conducted in order to predict the aerodynamic forces on the NP car. The turbulent air flow around the car is modeled using the realizable k-ε model. First, results are validated against those presented for the Ahmed’s body. Next, the fluid flow around the car is simulated for different car speeds ( to mph) and fl...

The interaction of the overlying turbulent flow with riblets, and its impact on their drag reduction properties are analysed. In the so-called viscous regime of vanishing riblet spacing, the drag reduction is proportional to the riblet size, but for larger riblets the proportionality breaks down, and the drag reduction eventually becomes an increase. It is found that the groove cross section A(...

there are different methods to reduce drag in high speed hulls. one of these methods is a change in the shape of the body by adding longitudinal side tunnels. in this paper it has been attempted to determine the influence of the tunnel height on hydrodynamic characteristics of the hull to achieving an optimum shape for the tunnel. to achieve this purpose, numerical simulation of the problem has...

Bioluminescence represents an operational threat to U.S. Navy nighttime operations because of the vulnerability risk due to detection because of flow-stimulated light emission from naturally occurring plankton. Conversely, bioluminescence presents additional capabilities for detecting moving objects at night, particularly in the littoral zone where conventional acoustic surveillance is severely...