coefficient distribution
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2021 ◽  
Vol 2021 ◽  
pp. 1-8
Moloud ArianMaram ◽  
Mahmoud Ghiasi ◽  
Hassan Ghassemi ◽  
Hamid Reza Ghafari

In this paper, two different 3D hydrofoils with profiles NACA0012 are simulated in the potential flow. Boundary element method (BEM) and nonuniform rational B-spline (NURBS) are coupled to reduce error and increase accuracy. The computer code is developed in different submergence depths (d), flow velocities (U), and various angles of attack (AoA), and the pressure is obtained by NURBS formulation. The pressure on a 3D hydrofoil with NACA412 profile iscompared with other existing methods. The validity of result is revealed. The accuracy of the results is acceptable. The competition of the two models’ results indicates that the increasing chord length leads to increase in C p min , and the decrease in depth and angle of attack leads to the growing value of C p min . Moreover, when the flow velocity is changed, the changes of potential and pressure coefficient distribution do not follow the specific trend. NURBS is a basic equation in different CAD packages because it is able to mesh surfaces. This study demonstrates that this algorithm does mesh surface of high quality, so it can be developed to generate mesh on the submerged three-dimensional bodies .

Mechanika ◽  
2021 ◽  
Vol 27 (4) ◽  
pp. 285-294
Zhenjun GAO ◽  
Jianbo ZHANG ◽  
Wenyang LI ◽  
Jintao LIU ◽  
Changqing SI ◽  

The medium in the cooling circulation channel of the magnetic drive centrifugal pump will take away the heat generated by the magnetic eddy current and bearing friction in time to avoid the high temperature demagnetization phenomenon of the permanent magnets. Therefore, the reasonable design of the cooling circulation channel directly affects the stable operation of the magnetic drive centrifugal pump. In this paper, the heat exchange and temperature distribution in the cooling circulating channel of magnetic drive pump are studied by means of numerical calculation of fluid-heat coupling and external characteristic test. The temperature distribution and development law of the isolation sleeve clearance, the bottom of the isolation sleeve and the reflow hole are analysed emphatically, and the convection heat transfer coefficient distribution in the isolation sleeve clearance is studied.

2021 ◽  
Shan Wang ◽  
C. Guedes Soares

Abstract Three-dimensional effects on slamming loads predictions of a ship section are investigated numerically using the unsteady incompressible Reynolds-Average Navier-Stokes (RANS) equations and volume of fluid (VOF) method, which are implemented in interDyMFoam solver in open-source library OpenFoam. A convergence and uncertainty study is performed considering different resolutions and constant Courant number (CFL) following the ITTC guidelines. The numerical solutions are validated through comparisons of slamming loads and motions between the CFD simulations and the available experimental values. The total slamming force and slamming pressures on a 2D ship section and the 3D model are compared and discussed. Three-dimensional effects on the sectional force and the pressures are quantified both in transverse and longitudinal directions of the body considering various entry velocities. The non-dimensional pressure coefficient distribution on the 3D model is presented.

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1027
Claudia Simone Plüisch ◽  
Rouven Stuckert ◽  
Alexander Wittemann

Differential centrifugal sedimentation (DCS) is based on physical separation of nanoparticles in a centrifugal field prior to their analysis. It is suitable for resolving particle populations, which only slightly differ in size or density. Agglomeration presents a common problem in many natural and engineered processes. Reliable data on the agglomeration state are also crucial for hazard and risk assessment of nanomaterials and for grouping and read-across of nanoforms. Agglomeration results in polydisperse mixtures of nanoparticle clusters with multimodal distributions in size, density, and shape. These key parameters affect the sedimentation coefficient, which is the actual physical quantity measured in DCS, although the method is better known for particle sizing. The conversion into a particle size distribution is, however, based on the assumption of spherical shapes. The latter disregards the influence of the actual shape on the sedimentation rate. Sizes obtained in this way refer to equivalent diameters of spheres that sediment at the same velocity. This problem can be circumvented by focusing on the sedimentation coefficient distribution of complex nanoparticle mixtures. Knowledge of the latter is essential to implement and optimize preparative centrifugal routines, enabling precise and efficient sorting of complex nanoparticle mixtures. The determination of sedimentation coefficient distributions by DCS is demonstrated based on supracolloidal assemblies, which are often referred to as “colloidal molecules”. The DCS results are compared with sedimentation coefficients obtained from hydrodynamic bead-shell modeling. Furthermore, the practical implementation of the analytical findings into preparative centrifugal separations is explored.

Saqib Jamshed ◽  
Amit Dhiman

Abstract The current research focuses on the laminar flow through permeable side-by-side bars of a square cross-section in a channel-confined domain. Vorticity generation on the leeward sides of the permeable bodies further necessitates the study for a better understanding of underlying physics. Reynolds number Re and Darcy number Da are varied from 5 to 150 and 10-6 to 10-2, respectively, at transverse gap ratios s/d=2.5-10. In the perspective of periodic unsteady flow, critical Re for the onset of vortex shedding is analyzed. Streamlines, vorticity, pressure coefficient distribution, and velocity profiles are discussed to identify the wake patterns. In lower permeability level, vortex-shedding from the permeable square cylinders is observed either in synchronized anti-phase mode or a single large vortex street with a synchronized in-phase pattern in the near wake. A steady-state wake pattern symmetric and flocked towards the centerline is observed for all s/d at a higher permeability level regardless of Re. Wake patterns are not altered for Da=10-6-10-3; instead, prompt extermination of the two vortex streets downstream is observed at Da=10-3 as compared to Da=10-6. The impact of s/d, Re, and permeability on the drag is examined. A jump in the flow characteristics and drag forces is noticed at higher Re for the mid-range Da remarkably at lower s/d. For the extent of high permeability, the drag coefficient asymptotically gets closer to zero.

InterConf ◽  
2021 ◽  
pp. 738-753
Masrur Mukhammadiev ◽  
Abdurakhim Avazov ◽  
Akhtamkhan Elmurodov ◽  
Numonjon Khaydarov

Today, acute pancreatitis remains one of the three leading reasons for hospitalization of patients in emergency departments. Despite the fact that the material and technical base of medical institutions is improving every year, it is not always possible to timely and adequately assess the severity of the condition of patients with acute pancreatitis. Underestimation of the severity of the condition can end up sadly for the patient, therefore, patients with severe acute pancreatitis should be identified in the early stages of the disease. To predict the severe course of acute pancreatitis in the early stages of the disease, it is necessary to take into account such risk factors as age, concomitant diseases, body mass index, as well as clinical and laboratory markers of severity: hematocrit, neutrophil-lymphocyte coefficient, distribution of erythrocytes by volume, glucose, urea and data from integral scales. Markers such as respiratory failure and oliguria diagnosed upon admission, as well as the level of lactate dehydrogenase, bicarbonates and acid-base balance of the blood, can also be considered prognostically significant markers of severe course. Early identification of patients with an increased risk of complications and their timely adequate therapy can improve treatment outcomes and reduce mortality rates.

Evergreen ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 193-197
Hiroshi Eshima ◽  
Naoki Ikegaya ◽  
Takuya Yasumasu ◽  
Aya Hagishima ◽  
Jun Tanimoto

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