Wen-Jei Yang

Bio: Wen-Jei Yang is an academic researcher from University of Michigan. The author has contributed to research in topics: Heat transfer & Monte Carlo method. The author has an hindex of 8, co-authored 10 publications receiving 315 citations.

Radiative heat transfer by the Monte Carlo method

Abstract: Part 1 Principles of radiation: thermal radiation radiation heat transfer. Part 2 Principles of Monte Carlo methods: formulation methods of solution special treatises. Part 3 Applications of the Monte Carlo method: two-dimensional systems some industrial applications references applications on disk list of variables in computer programs.

Monte Carlo method for radiative heat transfer analysis of general gas‐particle enclosures

Abstract: A new Monte Carlo method is developed to analyse multi-dimensional radiative heat transfer in an enclosure containing grey gas with anisotropically scattering grey particles. One set of variables, called READ (Radiative Energy Absorption Distribution), is introduced to represent radiative transfer, thus appreciably reducing repeated computations required by the conventional Monte Carlo technique. A 1 m × 1 m square duct is used as the enclosure with the upper and lower walls at different temperatures in the one-dimensional case and with adiabatic specular or diffuse side walls in the two-dimensional case. Results agree well with the existing analytical solutions for one-dimensional, non-scattering cases. It is concluded that, with anisotropic scattering, an increase in the absorption coefficient and/or single scattering albedo produces adverse effects on radiative heat transfer. Anisotropic scattering effects cannot be simulated by the use of the effective absorption coefficient.

Heat Transfer In High Technology And Power Engineering

Abstract: The text is divided into four parts: I, Heat Transfer in High Technology; II, High Heat-Flux Technology; III, High-Performance Heat Exchange Devices; IV, Radiative Heat Transfer and Solar Energy Utilization. The role of thermocapillary flow in heat transfer is studied in view of the importance in space processing, such as superpure crystal growth under reduced-gravity environment. Techniques of heat transfer and flow control in space machinery in Japan during the past five years are surveyed. These include thermal control in satellites, electric propulsion, and materials processing in space; flow behavior under microgravity; and space cryogenics. The application of heat pipes in cooling is extended to devices in space and terrestrial uses. Heat transfer related to materials processing, a subject of current interest, is represented by three articles dealing with heat bonding processes, molecular clustering, and the growth of large single crystals. Another subject of current importance is heat transfer in electronic equipment.

Recent advances in the use of infrared thermography

Abstract: Infrared thermography transforms the thermal energy, emitted by objects in the infrared band of the electromagnetic spectrum, into a visible image. This feature represents a great potentiality to be exploited in many fields, but this technique is still not adequately enclosed in industrial instrumentation because of a lack of adequate knowledge; at first sight, it seems too expensive and difficult to use. The aim of the present paper is to shortly overview existing work and to describe the most relevant experiences devoted to the use of infrared thermography in three main fields, i.e. thermo-fluid dynamics, technology and cultural heritage, which have been performed in the department the authors belong to. Results may be regarded from two points of view, either as validating infrared thermography as a full measurement instrument, or as presenting infrared thermography as a novel technique able to deal with several requirements, which are difficult to perform with other techniques. This study is also an attempt to give indications for a synergic use of the different thermographic methods and sharing experiences in the different fields.

The Monte Carlo Method in Radiative Heat Transfer

Abstract: The use of the Monte Carlo method in radiative heat transfer is reviewed. The review covers surface-surface, enclosure, and participating media problems. Discussio. is included of research on the fundamentals of the method and on applications to surface-surface interchange in enclosures, exchange between surfaces with roughness characteristics, determination of configuration factors, inverse design, transfer through packed beds and fiber layers, participating media, scattering, hybrid methods, spectrally dependent problems including media with line structure, effects of using parallel algorithms, practical applications, and extensions of the method. Conclusions are presented on needed future work and the place of Monte Carlo techniques in radiative heat transfer computations

Function of the Caudal Fin During Locomotion in Fishes: Kinematics, Flow Visualization, and Evolutionary Patterns1

Abstract: One of the most prominent characteristics of early vertebrates is the elongate caudal fin bearing fin rays. The caudal fin represents a fundamental design feature of vertebrates that predates the origin of jaws and is found in both agnathans and gnathostomes. The caudal fin also represents the most posterior region of the vertebrate axis and is the location where fluid, accelerated by movement of the body anteriorly, is shed into the surrounding medium. Despite the extensive fossil record of the caudal fin, the use of caudal characters for systematic studies, and the importance of tail function for understanding locomotor dynamics in fishes, few experimental studies have been undertaken of caudal fin function. In this paper I review two experimental approaches which promise to provide new insights into the function and evolution of the caudal fin: three-dimensional kinematic analysis, and quantitative flow measurements in the wake of freely-swimming fishes using digital particle image velocimetry (DPIV). These methods are then applied to the function of the caudal fin during steady swimming in fishes with heterocercal and homocercal morphologies: chondrichthyians (leopard sharks) and ray-fined fishes (sturgeon and bluegill sunfish). The caudal fin of leopard sharks functions in a manner consistent with the classical model of heterocercal tail function in which the caudal surface moves at an acute angle to the horizontal plane, and hence is expected to generate lift forces and torques which must be counteracted anteriorly by the body and pectoral fins. An alternative model in which the shark tail produces a reactive force that acts through the center of mass is not supported. The sturgeon heterocercal tail is extremely flexible and the upper tail lobe trails the lower during the fin beat cycle. The sturgeon tail does not function according to the classical model of the heterocercal tail, and is hypothesized to generate reactive forces oriented near the center of mass of the body which is tilted at an angle to the flow during steady locomotion. Functional analysis of the homocercal tail of bluegill shows that the dorsal and ventral lobes do not function symmetrically as expected. Rather, the dorsal lobe undergoes greater lateral excursions and moves at higher velocities than the ventral lobe. The surface of the dorsal lobe also achieves a significantly acute angle to the horizontal plane suggesting that the homocercal tail of bluegill generates lift during steady swimming. These movements are actively generated by the hypochordal longitudinalis muscle within the tail. This result, combined with DPIV flow visualization data, suggest a new hypothesis for the function of the homocercal tail: the homocercal tail generates tilted and linked vortex rings with a central jet inclined posteroventrally, producing an anterodorsal reactive force on the body which generates lift and torque in the manner expected of a heterocercal tail. These results show that the application of new techniques to the study of caudal fin function in fishes reveals a previously unknown diversity of homocercal and heterocercal tail function, and that morphological characterizations of caudal fins do not accurately reflect in vivo function.

Turbine blade film cooling using psp technique

Abstract: Film cooling is widely used to protect modern gas turbine blades and vanes from the ever increasing inlet temperatures. Film cooling involves a very complex turbulent flow-field, the characterization of which is necessary for reliable and economical design. Several experimental studies have focused on gas turbine blade, vane and end-wall film cooling over the past few decades. Measurements of heat transfer coefficients, film cooling effectiveness values and heat flux ratios using several different experimental methods have been reported. The emphasis of this current review is on the Pressure Sensitive Paint (PSP) mass transfer analogy to determine the film cooling effectiveness. The theoretical basis of the method is presented in detail. Important results in the open literature obtained using the PSP method are presented, discussing parametric effects of blowing ratio, momentum ratio, density ratio, hole shape, surface geometry, free-stream turbulence on flat plates, turbine blades, vanes and end-walls. The PSP method provides very high resolution contours of film cooling effectiveness, without being subject to the conduction error in high thermal gradient regions near the hole.