Z. C. Zheng

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Air flowing around the wing tips of an airplane forms horizontal tornado-like vortices that can be dangerous to following aircraft. The dynamics of such vortices, including ground and atmospheric effects, can be predicted by numerical simulation, allowing the safety and capacity of airports to be improved. In this payer, we introduce three-dimensional(More)
A thorough numerical analysis is performed for time-domain simulation of acoustic wave propagations in the atmosphere, with the ground modeled as a porous medium. Two types of computational grid arrangement for the simulation, i.e., the staggered grid and the collocated grid, are considered. It is proved that the computational schemes based on these two(More)
This paper was motivated by a computational effort to model the aircraft wake vortex hazard near airports. Those flows can usually be approximated as a pair of two-dimensional, incompressible vortices interacting with an infinite solid wall. The present numerical model uses a vorticity–streamfunction formulation to simulate the two-dimensional problem.(More)
Both compact Green's functions and asymptotic expansions are widely used to analytically predict sound generated by low Mach number ( 1 << M ) fluid-dynamic sources, where the acoustic compactness of the source region is satisfied. By mathematically investigating the detailed assumptions involved in each of the two methods and by using two classical(More)
A thin-tube vortex method is developed to investigate the intrinsic instability within a counter-rotating vortex pair system and the e ects from the core size and the wavenumbers (or wavelengths). The numerical accuracy and the advantages of the scheme are theoretically estimated. A nearest-neighbour-image method is employed in this three-dimensional vortex(More)
Hypothermia and venous thrombosis can cause complications during perioperative and postoperative periods which can even be fatal to patients' conditions. Separative devices have currently been used to prevent those two problems. The device proposed here is to combine in a simple unobtrusive fashion the desirable effects of both temperature control and deep(More)
  • Z. C. Zheng
  • Technology and health care : official journal of…
  • 2001
Because of complicated rheological issues related with sickle cell blood, there exists a practical need to rationally determine critical hematocrit in transfusions for sickle cell patients. In this research, two major effects, i.e. oxygen concentration and hematocrit, are considered in a theoretical hydrodynamic model incorporating oxygen transport and(More)