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Numerical Prediction of Induced Pressure and Lift of the Planing Surfaces

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China Ocean Engineering 2009年第2期23卷 221-232页

作者： Hassan ghassemi ahmad Reza KOHANSAL Mahmoud GHIASSI Department of Marine Technology Amirkabir Urdversity of Technology 15875-4413 Tehran Iran

This paper discusses the numerical prediction of the induced pressure and lift of the planing surfaces in a steady motion based on the potential flow solver as well as the spray drag by use of the practical method. The numerical method for computation of the induced pressure and lift is potential-based boundary element method. Special technique is identified to present upwash geometry and to determine the spray drag. Numerical results of a planing flat plate and planing craft model 4666 are presented. It is shown that the method is robust and efficient and the results agree well with the experimental measurements with various Froude numbers.

关键词： planing surface pressure distribution induced pressure drag and lift spray

Bedding plane-embedded augmented virtual internal bonds for fracture propagation simulation in shale

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Theoretical & Applied Mechanics Letters 2021年第3期11卷 180-185页

作者： Zihan Liu Zhennan Zhang ahmad ghassemi Department of Civil Engineering Shanghai Jiao Tong UniversityShanghai 200240China Mewbourne School of Petroleum and Geological Engineering The University of OklahomaNormanOK 73091USA

To effectively simulate the fracture propagation in shale,the bedding plane(BP)effect is incorporated into the augmented virtual internal bond(AVIB)constitutive relation through BP *** the BP-embedded AVIB with the theory of transverse isotropy,it is found the approach can represent the anisotropic properties induced by parallel *** the simulation example,it is found that this method can simulate the stiffness anisotropy of shale and can represent the effect of BPs on hydraulic fracture propagation *** with the BP-embedded virtual internal bond(VIB),this method can account for the various Poisson’s *** provides a feasible approach to simulate the fracture propagation in shale.

关键词： Shale Bedding plane Constitutive model Hydraulic fracture Augmented virtual internal bond

The viscous strip approach to simplify the calculation of the surface acoustic wave generated streaming

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Applied Mathematics and Mechanics(English Edition) 2024年第4期45卷 711-724页

作者： F.JAZINI DORCHEH M.ghassemi Fuel Cells and Nano Systems(FCNS)Laboratory Department of Mechanical EngineeringK.N.Toosi University of TechnologyTehran 19697Iran

In recent decades,the importance of surface acoustic waves,as a biocompatible tool to integrate with microfluidics,has been proven in various medical and biological *** numerical modeling of acoustic streaming caused by surface acoustic waves in microchannels requires the effect of viscosity to be considered in the equations which complicates the *** this paper,it is shown that the major contribution of viscosity and the horizontal component of actuation is concentrated in a narrow region alongside the actuation *** the inviscid equations are considerably easier to solve,a division into the viscous and inviscid domains would alleviate the computational load *** particles'traces calculated by this approximation are excellently alongside their counterparts from the completely viscous *** is also shown that the optimum thickness for the viscous strip is about 9-fold the acoustic boundary layer thickness for various flow patterns and amplitudes of actuation.

关键词： surface acoustic wave microfluidics numerical simulation particle tracing acoustic streaming

Isoparametric Boundary Element Method Applied to the Rectangular and Delta Hydrofoils near the Free Surface

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China Ocean Engineering 2010年第2期24卷 321-331页

作者： Hassan ghassemi ahmad Reza KOHANSAL Faculty of Marine Technology Amirkabir University of Technology

In this paper, the hydrodynamic characteristics and flow field around rectangular and delta hydrofoils, moving with a constant speed beneath the free surface are numerically studied by means of isoparametric boundary element method （IBEM）. The quantities （source and dipole strengths） and the geometry of the dements are represented by a linear distribution. Two types of three-dimensional hydrofoils （rectangular and delta） are selected with NACA4412 and symmetric Joukowski sections. Some numerical results of pressure distribution, lift, wave-making drag coefficients and velocity field around the hydrofoils are presented. Also, the wave pattern due to moving hydrofoil is predicted at different operational conditions. Comparisons are made between computational results obtained through this method and those from the experimental measurements and other numerical results which reveal good agreement.

关键词： isoparametric boundary element method delta and rectangular hydrofoils hydrodynamic characteristics free surface

High power density technologies for large generators and motors for marine applications with focus on electrical insulation challenges

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High Voltage 2020年第1期5卷 7-14页

作者： Mona ghassemi Department of Electrical and Computer Engineering Virginia Tech1185 Perry Street644 Whittemore HallBlacksburgVA 24061USA

High power density generators and motors are envisaged in modern all-electric ships where electrical power for both propulsion and service loads is provided through a common electrical platform known as an integrated power *** recent high-power density technologies for generators and motors proposed for marine applications are reviewed,and the author focuses on their electrical insulation *** technologies are high-frequency(high-speed)generators(200–400 Hz),superconducting generators,and novel insulation materials and *** high-speed generators,high loss in magnetic materials may shorten its insulation ***,these generators should be designed to be cooled by water instead of *** superconducting generators,the most significant concern is the integrity of the insulation system over the large thermal excursion whenever the system is cycled between room temperature and operating *** novel insulation materials and systems section:(i)using mica paper tapes containing boron nitride filler in the binding resin of the glass backing insulation,developed by Toshiba and Von Roll,resulted in a 15%increase in the MVA of generators for the same slot dimensions and operating temperatures,(ii)GE developed an enhanced polyethylene glycol terephthalate-mica tape having superior voltageendurance characteristics,(iii)Isovolta has introduced a mica paper tape using a flat glass fibre backing material,called Powerfab,rather than the more common woven structure,leading to a 15%reduced mica tape,and(iv)adding novel nanocomposites as fillers to ground wall insulation,introduced by Siemens,is a promising technique towards more high power density ***,accelerated aging of insulation systems especially those in electrical rotating machines exposed to voltage pluses with high slew rates up to hundreds of kV/μs and high-repetition rates ranging from hundreds of kHz to MHz is *** voltage pulses are generated by wide bandga

关键词： power insulation electrical

PD measurements,failure analysis,and control in high-power IGBT modules

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High Voltage 2018年第3期3卷 170-178页

作者： Mona ghassemi Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University(Virginia Tech)BlacksburgVA 24061USA

Increased voltage blocking capability and the development of packaging technology for IGBTs can enhance the local electric field that may become large enough to increase partial discharges(PDs)within the *** study presents a survey on(i)simulation the electric field within an IGBT module;(ii)current standards for evaluation of the insulation systems of IGBTs;(iii)PD detection and localisation methods as well as other diagnostic and quality control test methods about IGBTs;and(iv)various methods for PD control in an IGBT *** survey shows remarkable technical gaps in all four *** sophisticated numerical and theoretical techniques are needed to model complicated geometries,*** sharp edges of the copper metallisation and protrusions in the substrate,and composite non-linear field grading *** is no model to take into account defects in the gel and on the ceramic *** 61287-1 cannot sufficiently assess the behaviour of PDs on IGBT module under the actual operating conditions exposing fast rise pulse-width modulation-like *** is no agreement on the exact origin and location of PDs in the module with relying on measured phase-resolved PD *** control methods using non-linear grading materials are not mature enough.

关键词： enough insulation ceramic

Towards skin polarization characterization using polarimetric technique

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2009年第8期10卷 602-608页

作者： Pejhman ghassemi Mohammad Hossein MIRANBAYGI Biomedical Engineering Group Department of Electrical and Computer EngineeringTarbiat Modares University

Measurement of optical properties of skin is an expanding and growing field of *** studies have shown that the biological tissue,especially skin,changes the polarization state of the incident *** this property will enable the study of abnormalities and diseases that alter not only the light intensity but also its polarization *** this paper we report an experimental study for measuring changes of polarization state of the light scattered from a phantom similar to a sample model of scattering *** the notation of Stokes vector for the polarized light and Mueller matrix for the sample with its polarization properties,we have shown that some elements of the matrix were particularly sensitive to the changes of the polarization-altering physical properties of the scatterers within the phantom.

关键词： Polarization Skin Phantom Scattering polarimetry Mueller matrix Stokes vector

Microscopic and macroscopic atomization characteristics of a pressure-swirl atomizer, injecting a viscous fuel oil

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Chinese Journal of Chemical Engineering 2020年第1期28卷 9-22页

作者： Seyed Mohammad Ali Najafi Pouria Mikaniki Hojat ghassemi School of Mechanical Engineering Iran University of Science and Technology(IUST)P.O.B.16765-163TehranIran

Combustion of heavy fuels is one of the main sources of greenhouse gases, particulate emissions, ashes, NOxand SOx. Gasification is an advanced and environmentally friendly process that generates combustible and clean gas products such as hydrogen. Some entrained flow gasifiers operate with Heavy Fuel Oil(HFO) feedstock. In this application, HFO atomization is very important in determining the performance and efficiency of the *** atomization characteristics of HFO(Mazut) discharging from a pressure-swirl atomizer(PSA) are studied for different pressures difference(Δp) and temperatures in the atmospheric ambient. The investigated parameters include atomizer mass flow rate( _m), discharge coefficient(CD), spray cone angle(θ), breakup length(Lb), the unstable wavelength of undulations on the liquid sheet(λs), global and local SMD(sauter mean diameter) and size distribution of droplets. The characteristics of Mazut sheet breakup are deduced from the shadowgraph technique. The experiments on Mazut film breakup were compared with the predictions obtained from the liquid film breakup model. Validity of the theory for predicting maximum unstable wavelength was investigated for HFO(as a highly viscous liquid). A modification on the formulation of maximum unstable wavelength was presented for HFO. SMD decreases by getting far from the atomizer. The measurement for SMD and θ were compared with the available correlations. The comparisons of the available correlations with the measurements of SMD andθ show a good agreement for Ballester and Varde correlations, respectively. The results show that the experimental sizing data could be presented by Rosin-Rammler distributions very well at different pressure difference and temperatures.

关键词： Gasifier Heavy fuel oil Atomization Pressure-swirl atomizer Mazut Size distribution Wavelength Viscosity

Effect of Chromite-Silica Sands Characteristics on Performance of Ladle Filler Sands for Continuous Casting

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Journal of Iron and Steel Research International 2012年第3期19卷 11-13,19页

作者： F Farshidfar M ghassemi Kakroudi Materials Science and Engineering Department University of Tabriz

Free opening rate is mainly determined by the performance of the ladle filler sand. High free opening rates of ladles are required in steel making to improve steel quality. Chromite ladle filler sands are one of the most widely used ladle filler sand. Several operative variables and materials characteristics affect the performance of the sands. Three sets of chromite ladle filler sands were selected and researches were focused on the sintering hehaviour and per- formance of the sands under operative conditions. The effect of particle size distribution on sintering, microstruc- ture, flowability, and permeability were presented. In all cases, the particle size varies from 0.1 to 1.5 mm corre- sponding to free flowing powders. One of the samples has higher permeability factor in comparison with others due to low particle size distribution. The other sample presents very good free opening due to its very good flowability and permeability factor.

关键词： nozzle filler sand chromite based sand sintering behavior penetration depth