A. G. Fabula

Bio: A. G. Fabula is an academic researcher. The author has contributed to research in topics: Lift-to-drag ratio & Airfoil. The author has an hindex of 1, co-authored 1 publications receiving 27 citations.

Thin-airfoil theory applied to hydrofoils with a single finite cavity and arbitrary free-streamline detachment

Abstract: Thin-airfoil theory is applied to steady, plane potential flow about vented or cavitating hydrofoils of arbitrary profile when there are two free-streamlines detaching from the foil and bounding the single cavity that extends downstream of the trailing edge. Cavity-termination models employed are the closed, the partly closed and the open models for which the thickness of the implied ’wake’ following the cavity ranges from zero to maximum for the open model. The general solution for given wetted-surface profile, cavity length and particular cavity termination is constructed by superposition of the profile's cusp-closure solution (angle of attack α+) plus the particular flat-plate solution to give the desired angle of attack α. Four related integrals involving the wetted-surface contour slope distribution lead to drag, lift, cavity pressure and α+ vs cavity length. A comparison of theoretical and experimental lift and drag for a cavitating hydrofoil shows good agreement until the theoretical cavity closure nears the trailing edge.

Cavitation and Bubble Dynamics

Abstract: This book describes and explains the fundamental physical processes involved in bubble dynamics and the phenomenon of cavitation. It is intended as a combination of a reference book for those scientists and engineers who work with cavitation or bubble dynamics and as a monograph for advanced students interested in some of the basic problems associated with this category of multiphase flows. A basic knowledge of fluid flow and heat transfer is assumed but otherwise the analytical methods presented are developed from basic principles. The book begins with a chapter on nucleation and describes both the theory and observations of nucleation in flowing and non-flowing systems. The following three chapters provide a systematic treatment of the dynamics of the growth, collapse or oscillation of individual bubbles in otherwise quiescent liquids. Chapter 4 summarizes the state of knowledge of the motion of bubbles in liquids. Chapter 5 describes some of the phenomena which occur in homogeneous bubbly flows with particular emphasis on cloud cavitation and this is followed by a chapter summarizing some of the experiemntal observations of cavitating flows. The last chapter provides a review of the free streamline methods used to treat separated cavity flows with large attached cavities.

A numerical nonlinear analysis of the flow around two- and three-dimensional partially cavitating hydrofoils

Abstract: The partially cavitating two-dimensional hydrofoil problem is treated using nonlinear theory by employing a low-order potential-based boundary-element method. The cavity shape is determined in the framework of two independent boundary-value problems; in the first, the cavity length is specified and the cavitation number is unknown, and in the second the cavitation number is known and the cavity length is to be determined. In each case, the position of the cavity surface is determined in an iterative manner until both a prescribed pressure condition and a zero normal velocity condition are satisfied on the cavity. An initial approximation to the nonlinear cavity shape, which is determined by satisfying the boundary conditions on the hydrofoil surface rather than on the exact cavity surface, is found to differ only slightly from the converged nonlinear result.The boundary element method is then extended to treat the partially cavitating three-dimensional hydrofoil problem. The three-dimensional kinematic and dynamic boundary conditions are applied on the hydrofoil surface underneath the cavity. The cavity planform at a given cavitation number is determined via an iterative process until the thickness at the end of the cavity at all spanwise locations becomes equal to a prescribed value (in our case, zero). Cavity shapes predicted by the present method for some three-dimensional hydrofoil geometries are shown to satisfy the dynamic boundary condition to within acceptable accuracy. The method is also shown to predict the expected effect of foil thickness on the cavity size. Finally, cavity planforms predicted from the present method are shown to be in good agreement to those measured in a cavitating three-dimensional hydrofoil experiment, performed in MIT's cavitation tunnel.

Characteristics of forced convection heat transfer in vertical internally finned tube

Abstract: This work presents a numerical investigation of a vertical internally finned tube subjected to forced convection heat transfer. The governing equations were solved numerically using the control volume technique. Nusselt number, Nu, and friction factor multiplied by Reynolds number, fRe, are influenced greatly by the height and number of the radial fins. The velocity and temperature distributions inside the tube depend on the number and height of the radial fins. This paper suggests that for best heat transfer to be achieved there is an optimum combination of fin numbers and height. D 2004 Elsevier Ltd. All rights reserved.