The thrust-generating mechanism of a prolate hydromedusa Sarsia tubulosa and an oblate hydromedusa Aequorea victoria was investigated by solving the incompressible Navier-Stokes equations in the swirl-free cylindrical coordinates. The calculations clearly show the vortex dynamics related to the thrust-generating mechanism, which is very important for understanding the underlying propulsion mech...

Compact zero-mass pulsatile jet actuators are proposed for low-speed maneuvering and station keeping of small underwater vehicles. The flow field of such jets are initially dominated by vortex ring formation. Pinched-off vortices characterize the extremum impulse accumulated by the leading vortex ring in a vortex ring formation process. Relevant parameters in this process are identified in orde...

The HH 34 superjet shows a steep velocity decrease (from ∼ 500 to ∼ 100 km s−1) over a distance of ∼ 2 pc on either side of the central source. We explore whether or not this behaviour could be interpreted as evidence for a slow “turning on” of the ejection velocity of the jet, and find that this is indeed possible, but only for an ejection velocity that has had a dramatic growth over the last ...

CL, CD, CD0 = lift coefficient, drag coefficient, and drag coefficient with zero lift DSi = dynamic soaring number sample E, Emin = aircraft total energy and minimum sustainable total energy, J g = gravity acceleration, m∕s h, hmin = altitude and safety altitude, m K = drag-polar-induced drag gain k1, k2, k3 = necessary and sufficient conditions inequality parameters L, D = lift and drag forces...

Abstract With the purpose of investigating effects geometry parameters CFJ (Coflow jet) device on aerodynamic characteristics supercritical bacj airfoil used by a STOL transport, we have carried out computational analysis with different values injection slot size and location under low-speed condition. The results show that lift coefficient decreases gradually decreasing stall angle, when is in...

This paper describes the development of the second‐generation Spherical Underwater Robot (SUR‐II). The new SUR‐II has an improved propulsion system structure, resulting in better performance compared with the original design. This paper focuses on the characteristics of the water‐jet thruster and the spherical hull of the SUR‐II. To analyse its hydrodynamic charac...

Because the amount of fuel usage is huge, and exhaust emissions of commercial transports is regulated under the Kyoto Protocol, how to reduce fuel consumption is an urgent problem for all airlines. The airlines urgently need a practical method to reduce fuel consumptions within constraints to accomplish the mission. The objective for the present paper is to use a model-based method and flight d...

We make use of the AdS/CFT correspondence to determine the energy of an external quark-antiquark pair that moves through strongly-coupled thermal N = 4 super-Yang-Mills plasma. It is found that the pair feels no drag force, has an energy that reproduces the expected √ 1− v/L behavior at small quarkantiquark separations, and becomes unbound beyond a certain screening length whose velocity-depend...