Drag Characteristics of Objects in Two-phase Boiling Flows
One aspect ot boiling that has received little investigation is the effect of boiling on the fluid-dynamic drag on objects. In addition to enhancing our understanding of the boiling processes, this aspect has been identified to have some scientific applications in nuclear safety analyses. A theoretical analysis of the drag characteristics of objects in two-phase boiling flows is presented and a theoretical model is developed to quantify the drag characteristics in the film boiling regime. The geometries investigated include a flat plate, wedge, circular cylinder and a sphere. The latter two geometries are considered in the context of film boiling form drag. The results of this dissertation effort indicate (for a water-steam system at atmospheric pressure) that the skin friction coefficient parameter on a flat plate or a wedge in a laminar film boiling flow may increase, remain the same or decrease beyond the single-phase flow level, depending upon free stream velocity, surface temperature, geometry, orientation and liquid subcooling. The external pressure gradient and or the stream-wise buoyancy force driving the vapor film may cause the skin friction coefficient to exhibit a "drag bucket type phenomenon" at increased wall temperatures.
Doctor of Philosophy (Ph.D.)
College of Engineering
Mechanical Engineering and Aerospace Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Dissertations, Academic -- Engineering; Engineering -- Dissertations, Academic
Chappidi, Padmanabha R., "Drag Characteristics of Objects in Two-phase Boiling Flows" (1989). Retrospective Theses and Dissertations. 4115.