Editor-in-Chief: Dr. S.D. Sharma
published quarterly ISSN 1756-8315 2015 journal prices/format options
2015 is volume 7
The domain of fluid sciences is vast. The more we explore, the more we discover its omnipresence influencing our everyday life. It is therefore not surprising that over the years there has been a steady and significant rise in the number of journals that publish numerous fluid related research articles spanning various disciplines of physics, engineering and biology. Being both multidisciplinary and interdisciplinary in nature, the subject of fluid mechanics provides boundless opportunities for research with multitude scales ranging from a few nanometers in the field of biofluid mechanics to the several kilometers encountered in the field of environmental fluid mechanics.
While the overall research contributions in the field of fluid mechanics have been overwhelming, there are some emerging areas that are making rapid progress and need special attention. In fact, a host of journals publishing without distinguishing between these two make it difficult for the fluid mechanics community, the contributors as well as the readers, to choose a journal for a particular emerging area.
It is therefore appropriate to start a new journal, which will act as a source for dissemination of the latest information on research advances in the following specific emerging areas.
Biofluid mechanics: complex movement of biological fluids, cardiovascular and pulmonary systems, development of prostheses and study of their behavior, blood pumps, microfluidic filter systems, drug delivery, etc. Nano and Micro fluid mechanics: micro-electro-mechanical systems (MEMS), nanofluidics, microfluids, microchannel flows, spray and aerosols, etc. Thermal fluid mechanics: combustion instability, cooling of electronics chips, heat transportation, etc. Engineering fluid mechanics: synthetic jets, vortex flows, drag reduction, road vehicles and train aerodynamics, turbulent mixing, wind turbines, control of flow separation, etc. Environmental fluid mechanics: atmospheric boundary layer, oceanic waves, wind induced avalanche, tornados, hurricane, cloud dynamics, pollutants dispersion, etc.
Geological fluid science: influence of water and other fluids in earth's crustal processes including the movement of chemicals and heat - believed to be responsible for seismic and volcanic activities which could also cause tsunami; effect of pore fluid pressure on fracturing of rocks, etc.
Convective precipitating systems: A review of associated thermodynamics
and moist potential vorticity (MPV)
Peter J. Lamb, NOAA Cooperative Institute for Mesoscale Meteorological Studies(CIMMS)
The University of Oklahoma, Norman, OK, USA
Guojun Gu, NASA/Goddard Space Flight Center, Greenbelt, MD, USA
Current theoretical understanding of convective precipitating systems is reviewed through a view of their associated thermodynamics and moist potential vorticity (MPV) dynamics. (1) Classic, saturated moist processes are first discussed, followed by the introduction of a new thermodynamic variable: the generalized potential temperature (q*). It is shown that q* can describe the so-called non-uniformly saturated moist processes more accurately than several widely used quantities including equivalent potential temperature (qe), virtual potential temperature (qv). (2) The convective available potential energy (CAPE), an important measure of potential convective instability, and the means to estimate it in reality are summarized next. In particular, how to include the effects of gravitational drag of cloud and precipitating particles, and precipitation-associated downdraft is discussed. (3) MPV dynamics and its application in convective precipitating systems are reviewed. We are specifically focused on the recently accomplished research work, including assessing the impact of precipitation-induced mass forcing on MPV and introducing two dynamic concepts: the generalized moist potential vorticity (GMPV) and convective vorticity vector (CVV). GMPV and CVV are further shown to be valuable in diagnosing moist saturated processes in convective precipitating systems.
A Modeling Study of Three-Dimensional Convective Vorticity Vector Associated
with a Heavy Rainfall Event
Gao Shouting, Lingkun Ran, Laboratory of Cloud-Precipitation Physics and Severe Storms
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
Xiaofan Li, Joint Center for Satellite Data Assimilation and NOAA/NESDIS/Center for Satellite Applications and Research, Camp Springs, Maryland
A three-dimensional convective vorticity vector is introduced to study a heavy rainfall event in the Huabei region of China based on the simulation data from the Advanced Regional Prediction System (ARPS) model. The simulation is validated with the observation data in terms of surface rainfall, dynamic and thermodynamic fields, which shows a fair agreement between simulations and observations. The time evolution and spatial distribution of three components of convective vorticity vector, potential vorticity, and cloud hydrometeors are calculated and a linear correlation analysis is carried out. The relationship between the vertical component of convective vorticity vector and cloud hydrometeors shows the highest linear correlation coefficient. The tendency equation of vertical component of convective vorticity vector is derived and the tendency budget is analyzed with the calculations of linear correlation coefficients and root-mean-squared differences. The covariance between vorticity and diabatic heating is primary factor for explaining the tendency of vertical component of convective vorticity vector. The results here with those in Gao et al. (2004, 2006) indicate that the convective vorticity vector is an important physical vector for studying both two- and three dimensional convective systems in tropics and mid-latitudes.
CONSTRUCTAL COOLING CHANNELS: APPLICATION TO HEAT TRANSFER IN MICRO-CHANNEL
T. Bello-Ochende and J. P. Meyer, Department of Mechanical and Aeronautical Engineering
University of Pretoria, 0002, Pretoria, South Africa
This paper reports on the geometric optimization of a three-dimensional micro-channel heat sink. Two types of micro-channel heat sinks configuration were studied. In both cases the objectives is to maximize the global thermal conductance subject to a fixed volume, high conducting material and a fixed pressure drop. In the first configuration the micro-channel is completely embedded inside a high conducting material and numerical simulations were carried out on a unit cell with volume ranging from 0.1 to 0.9 mm3 and pressure drop between 10 and 75 kPa. The axial length of the micro-channel heat sink was fixed at 10 mm. The cross-sectional area of the micro-channel heat sink is free to morph with respect to the degree of freedoms provided by the aspect ratio and the solid volume fraction. The effects of the total solid volume fraction and the pressure drop on the aspect ratio, channel hydraulic diameter and peak temperature are investigated. In the second configuration the micro-channels are embedded inside a high conducting material, except that the top is covered with an insulating material. The whole configuration was allowed to morph with respect to all the degrees of freedom. Similar but dimensionless numerical simulations were carried out on this configuration and the numerical optimization results were reported. In the first configuration numerical results show that the degrees of freedom have a strong effect on the peak temperature and the maximum thermal conductance. The optimal geometric characteristics (aspect ratio and the optimal channel shape) are reported and compared with those obtained from approximate relationships using scale analysis. For this configuration the predicted trends are found to be in good agreement with the predicted results. In the second configuration a test case on an actual micro-channel heat sink shows a reduction of about 8% in global thermal resistance.
THE STATISTICAL EVOLUTION OF A STRATIFIED SHEAR LAYER WITH HORIZONTAL SHEARS
Basak and S. Sarkar, Department of Mechanical and Aerospace Engineering, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
Direct numerical simulation (DNS) is used to investigate a shear layer with
horizontal shear in a stably stratified environment. Layers with horizontal
shear, although often observed in the ocean and the atmosphere, have received
much less attention than the corresponding case of vertical shear. The structural
organization of the instantaneous vorticity, density and dissipation fields
was reported previously by Basak and Sarkar, J. Fluid Mechanics (2006). The
effect of stratification on the statistical evolution of the shear layer is
examined in the
present paper. The profiles of the horizontal velocity variances show larger peak values as well as larger width relative to the unstratified situation. The peak value of vertical velocity variance decreases substantially owing to stable stratification although its width is larger. The increased width of the velocity variance profiles is due to intrusions and internal waves at the edges of the shear layer. There is significant buoyancy flux even at large stratification. Molecular mixing, measured by the dissipation rates of turbulent kinetic energy and potential
energy, also remains significant. The gradient statistics are dominated by vertical gradients leading to high anisotropy of the dissipation rates. Integral and dissipative length scales of turbulence are investigated as well as buoyancy related quantities such as the Ozmidov and Ellison lengths. The Ozmidov scale becomes smaller than the Ellison length scale. The behavior of length scales suggests that density perturbations are not associated with vertical overturns as in strong, mechanically driven turbulence but rather with local distortions of isopycnals by the coherent vortical structures in the flow.
Miniature Fluidic Devices: A Review of Development and Applications
Ganesh Raman, Illinois Institute of Technology
James Gregory, The Ohio State University
Surya Raghu, Advanced Fluidics LLC
Fluid logic circuits and fluidic sub-elements have been in use for over 70 years. However, with advances in miniaturization new designs that can be integrated to practical applications have emerged. This paper provides a brief review of such miniature devices that can provide oscillatory flow with no moving parts over a range of frequencies. In addition they can produce output signals of various waveforms and be arranged in arrays to perform specific tasks. The review also discussed methods of characterizing miniature fluidic actuators using high speed photography, pressure sensors, hot-wires and global measurements such as Pressure Sensitive Paint (PSP). The process of luminescence and oxygen quenching is employed by the PSP to measure surface pressure. Traditionally polymer binder was used as PSP but due to its slow response time porous PSP was used in the present work. There are three types of porous PSP 1) Anodized aluminium PSP (AA-PSP) 2) Thin layer-chromatography PSP (TLC-PSP) and 3) Polymer/Ceramic PSP (PC-PSP). Previous studies showed that AA-PSP had superior frequency response characteristics. So for the present study this PSP was chosen. Application examples include Jet mixing enhancement, Jet thrust vectoring and Cavity noise suppression. In the cavity noise application the acoustic levels were suppressed by 10 dB with only 0.12% of the main jet flow being injected through the fluidic actuators. We have grounds to believe that numerous future applications exist for such miniaturized fluidic actuators.
Nonlinear receptivity: TS Wave to Bypass Transition
T.K. Sengupta, Swagata Bhaumik, Vikram Singh & Sarvagy Shukl, Dept. of Aerospace Engineering, Indian Institute of Technology Kanpur, Kanpur 208 016, INDIA
Flow transition and the problem of turbulence continue to be the pacing item in furthering our understanding of fluid dynamics. For the transition problem, the role of the spectrum of the input disturbance on the dynamical system is appreciated in the subject area of receptivity- mainly through the study of linearized system. For low amplitude of a monochromatic excitation field, one notices the presence of Tollmien-Schlichting (TS) waves as a precursor to transition. While it is understood in a qualitative sense that with the increase in the strength of the input, one can bypass the formation of TS waves altogether, before transition occurring very rapidly. In the present work, a detailed set of results has been presented that explain both the routes via an innovative receptivity study by the solution of full Navier-Stokes equation subject to different amplitude of the excitation field.
FLOW-INDUCED ACOUSTIC RESONANCE AROUND A LONG FLAT PLATE IN A DUCT
Mikhail M. Katasonov*, Hyung Jin Sung‹ and Sergey P. Bardakhanov*
* Institute of Theoretical and Applied Mechanics SB RAS, Institutskaya 4/1, Novosibirsk, 630090, Russia
‹Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon, 305-701, Korea
Flows around long thin blunt flat plates generate acoustic resonances when the sound frequency generated by the vortex shedding is closer to the frequency of the acoustic modes around the plate. After their mutual capturing, the sound intensity strongly increases. To better understand this phenomenon, here we investigated the interaction between flow and flow induced acoustic resonance around a long flat plate in a duct. Three acoustic resonance modes were observed as the free-stream flow velocity was increased. The acoustic resonance behavior was studied as a function of the shapes of the leading and trailing edges (semicircular and square) and the length of the plate (39 Ť L/d Ť 71). The Reynolds numbers based on the plate thickness and flow velocity ranged from 3,300 to 21,300. The influence of the leading edge separation bubble and the trailing edge wake flow on the acoustic resonance was scrutinized by examining the velocity profiles, power spectra and pressure sound level. The strongly nonlinear behavior of the flow structure in the wake was shown at monochromatic sound resonance regime. Different shapes of the leading and trailing edges showed different efficiency of the sound-flow interaction and different sound levels. We found that the configuration with a semicircular leading edge and a semicircular trailing edge was the best for generating aeroacoustic resonance.
Dr. S.D. Sharma,
Department of Aerospace Engineering, Indian Institute of Technology Bombay,
Powai, Mumbai 400076, India
Sampath Kumar Arkalgud, All India Institute of Medical Sciences, India
Robert Breidenthal, Department of Aeronautics and Astronautics, College of Engineering, University of Washington, Seattle, WA 98195-2400, USA
Shouting Gao, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
Girija Jayaraman, Indian Institute of Technology, India
Satoyuki Kawano, Department of Mechanical Science and Bioengineering, Osaka University, Japan
Josua Petrus Meyer, Department of Mechanical and Aeronautical Engineering, University of Pretoria, South Africa
Andrew Seng Hock Ooi, Department of Mechanical Engineering, University of Melbourne, Australia)
Ganesh Raman, Illinois Institute of Technology, Chicago, IL 60616, USA
Tapan Sengupta, Department of Aerospace Engineering, Indian Institute of Technology, Kanpur, India
Sutanu Sarkar, Department of Mechanical and Aerospace Engineering, University of California at San Diego
Hyung Jin Sung, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Republic of Korea
Olaf Wünsch, Institute of Mechanics, University of Kassel, Germany
Charles Chun Yang, School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore
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