Computing the forces acting from a surrounding air phase onto a particle-based fluid or rigid object is challenging. Simulating the air phase and modeling the interactions using a multiphase approach is computationally expensive. Furthermore, stability issues may arise in such multiphase simulations. In contrast, the effects from the air can be approximated efficiently by employing a drag equat...

The main aim of this study was to investigate the effect of finger spread on the propulsive force production in swimming using computational fluid dynamics. Computer tomography scans of an Olympic swimmer hand were conducted. This procedure involved three models of the hand with differing finger spreads: fingers closed together (no spread), fingers with a small (0.32 cm) spread, and fingers wit...

In many applications the flow that past bluff bodies has frequency nature (oscillated) and it is not uniform. This kind of flow has effects on the formation of vortex shedding behind bluff bodies. In this paper the flow around a circular cylinder was numerically simulated. The effects of frequency variation at inlet flow on the vortex shedding frequency were investigated. The transient Two-Dime...

[1] The correct representation of the 10-m drag coefficient for momentum (K10) at extreme wind speeds is very important for modeling the development of tropical depressions and may also be relevant to the understanding of other intense marine meteorological phenomena. We present a unified boundary layer model for (K10), which takes account of both the wave field and spray production, and asympt...

The FRAGHAZ computer program has been developed to predict the hazardous regions due to fragments produced by an accidential explosion of stored ammunition. Determination of these hazardous regions is based on computer simulations of fragment trajectories. Currently, the fragment drag coefficients used in the program are extrapolations of subsonic drag coefficients out to transonic and superson...

We investigate the phenomenon of drag reduction in a viscoelastic fluid model of dilute polymer solutions. By means of direct numerical simulations of the three-dimensional turbulent Kolmogorov flow we show that drag reduction takes place above a critical Reynolds number Re(c). An explicit expression for the dependence of Re(c) on polymer elasticity and diffusivity is derived. The values of the...

Gliding flight performance and wake topology of a common swift (Apus apus L.) were examined in a wind tunnel at speeds between 7 and 11 m s(-1). The tunnel was tilted to simulate descending flight at different sink speeds. The swift varied its wingspan, wing area and tail span over the speed range. Wingspan decreased linearly with speed, whereas tail span decreased in a nonlinear manner. For ea...

A polynomial is determined by its roots and its leading coefficient. If you set the roots in motion, the critical points will move too. Using only tools from the undergraduate curriculum, we find an inverse square law that determines the velocities of the critical points in terms of the positions and velocities of the roots. As corollaries we get the Polynomial Root Dragging Theorem and the Pol...

This paper applies a Reinforcement Learning methodology to the problem of airfoil morphing. The reinforcement learning as it is applied to morphing is integrated with a computational model of an airfoil. The computational model utilizes a doublet panel method whose end yield is airfoil lift, drag, and moment coefficients. An episodic unsupervised learning simulation using the Q-Learning method ...

In this paper, the sediment-laden flow around a circular cylinder is numerically simulated in order to obtain better understanding of hydrodynamics associated. A range of cases with different Reynolds numbers (Re) are studies. The effects of the concentration of the sediment on the drag coefficient are investigated. Results show that due to the fact that the laden sand particle colliding the cy...