scholarly journals OPEN TYPE QUAY STRUCTURES UNDER PROPELLER JETS

2012 ◽  
Vol 1 (33) ◽  
pp. 19 ◽  
Author(s):  
Yalcin Yuksel ◽  
Selahattin Kayhan ◽  
Yesim Celikoglu ◽  
Kubilay Cihan
Keyword(s):  
Flow Characteristics ◽  
Structure Design ◽  
Shear Stresses ◽  
Flow Area ◽  
Open Type ◽  
Sea Bed ◽  
Cylindrical Piles ◽  
New Type ◽  
Hot Film ◽  
Bed Shear Stresses

In recent years, dramatically increases in ship dimensions and installed engine power, introduction of new type of special purpose ships and use of roll-on/roll-of, ferries, container ships can cause damage which in many cases threatens to undermine berth structures. Vessel jets of these types of ships can change flow area and cause erosion and scour around foundation of berth structures. Due to the damages in berth structures maintenance and repair cost may increase and also cause management losses. For this reason vessel jet induced the flow area around the berth structures during ships berthing and un-berthing operations are extremely important factor for the port structure design. This study is related with investigation of the flow characteristics at the sea bed around the pile, experimentally. Vessel jets were simulated both as circular wall jet and also propeller jet. The objective of this study is to determine the sea bed shear stress and velocity profiles along the jet axis for open type wharf structures (around a cylindrical piles and also on the slopes). Hot film anemometers were used to measure the magnitude of the bed shear stresses. The results from propeller jet experiments explained the erosion over the slopes. Bed shear and velocity profile measurements were carried out on the rigid bed conditions.

scholarly journals INTERFACIAL AND BED SHEAR STRESSES IN SALINE WEDGES

1982 ◽  
Vol 1 (18) ◽  
pp. 149
Author(s):  
Vassilios Dermissis ◽  
Emmanuel Partheniades
Keyword(s):  
Equations Of Motion ◽  
Dimensionless Number ◽  
Shear Stresses ◽  
Densimetric Froude Number ◽  
Families Of Curves ◽  
Data Points ◽  
Laboratory Investigations ◽  
Hot Film ◽  
Bed Friction ◽  
Bed Shear Stresses

The shear stresses and the associated friction coefficients at the interface and at the bed of an arrested saline wedge have been studied experimentally together with the detailed flow structure. Interfacial stresses, evaluated from hot film anemometer measurements and actual velocity profiles, agree well with those based on the integration of the equations of motion while the simplified one dimensional analysis gave considerably higher values, It_was found that both the average interfacial friction coefficient, f and the average bed friction factor, f are best correlated with the dimensionless number, ReFr2, where Re and Fr are the Reynolds number and the non-densimetric Froude number of the flow respectively, and with the relative density difference, Ap/p, The results are presented in two families of curves with Ap/p as a parameter. The scattering of data points is minimal and the agreement with the results of some previous laboratory investigations and field data is good.

scholarly journals Morphology Development and Flow Characteristics during High Moisture Extrusion of a Plant-Based Meat Analogue

Foods ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1753
Author(s):  
Patrick Wittek ◽  
Felix Ellwanger ◽  
Heike P. Karbstein ◽  
M. Azad Emin
Keyword(s):  
Transition Zone ◽  
Flow Characteristics ◽  
Phase System ◽  
Shear Stresses ◽  
High Moisture ◽  
Tensile Stresses ◽  
Morphology Development ◽  
A Minor ◽  
Multi Phase ◽  
High Moisture Extrusion

Plant-based meat analogues that mimic the characteristic structure and texture of meat are becoming increasingly popular. They can be produced by means of high moisture extrusion (HME), in which protein-rich raw materials are subjected to thermomechanical stresses in the extruder at high water content (>40%) and then forced through a cooling die. The cooling die, or generally the die section, is known to have a large influence on the products’ anisotropic structures, which are determined by the morphology of the underlying multi-phase system. However, the morphology development in the process and its relationship with the flow characteristics are not yet well understood and, therefore, investigated in this work. The results show that the underlying multi-phase system is already present in the screw section of the extruder. The morphology development mainly takes place in the tapered transition zone and the non-cooled zone, while the cooled zone only has a minor influence. The cross-sectional contraction and the cooling generate elongational flows and tensile stresses in the die section, whereas the highest tensile stresses are generated in the transition zone and are assumed to be the main factor for structure formation. Cooling also has an influence on the velocity gradients and, therefore, the shear stresses; the highest shear stresses are generated towards the die exit. The results further show that morphology development in the die section is mainly governed by deformation and orientation, while the breakup of phases appears to play a minor role. The size of the dispersed phase, i.e., size of individual particles, is presumably determined in the screw section and then stays the same over the die length. Overall, this study reveals that morphology development and flow characteristics need to be understood and controlled for a successful product design in HME, which, in turn, could be achieved by a targeted design of the extruders die section.

Dynamic Characteristics Analysis of Cable-Rib Tension Deployable Antenna

2016 ◽  
Author(s):  
Liu Ruiwei ◽  
Hongwei Guo ◽  
Zhang Qinghua ◽  
Rongqiang Liu ◽  
Tang Dewei
Keyword(s):  
Dynamic Characteristics ◽  
Structural Parameters ◽  
Element Model ◽  
Structure Design ◽  
Antenna Structure ◽  
Characteristics Analysis ◽  
New Type ◽  
Dynamic Characteristics Analysis ◽  
The Finite Element Model ◽  
Weight Dynamic

Balancing stiffness and weight is of substantial importance for antenna structure design. Conventional fold-rib antennas need sufficient weight to meet stiffness requirements. To address this issue, this paper proposes a new type of cable-rib tension deployable antenna that consists of six radial rib deployment mechanisms, numerous tensioned cables, and a mesh reflective surface. The primary innovation of this study is the application of numerous tensioned cables instead of metal materials to enhance the stiffness of the entire antenna while ensuring relatively less weight. Dynamic characteristics were analyzed to optimize the weight and stiffness of the antenna with the finite element model by subspace method. The first six orders of natural frequencies and corresponding vibration modes of the antenna structure are obtained. In addition, the effects of structural parameters on natural frequency are studied, and a method to improve the rigidity of the deployable antenna structure is proposed.

Endwall Boundary Layer Development in a Multistage Low-Speed Compressor With Tandem Stator Vanes

2021 ◽  
Author(s):  
Michael Hopfinger ◽  
Volker Gümmer
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Shear Stresses ◽  
Flow Area ◽  
Stage Design ◽  
Low Speed ◽  
Boundary Layer Development ◽  
Viscous Shear ◽  
Layer Development ◽  
Highly Loaded

Abstract The development of viscous endwall flow is of major importance when considering highly-loaded compressor stages. Essentially, all losses occurring in a subsonic compressor are caused by viscous shear stresses building up boundary layers on individual aerofoils and endwall surfaces. These boundary layers cause significant aerodynamic blockage and cause a reduction in effective flow area, depending on the specifics of the stage design. The presented work describes the numerical investigation of blockage development in a 3.5-stage low-speed compressor with tandem stator vanes. The research is aimed at understanding the mechanism of blockage generation and growth in tandem vane rows and across the entire compressor. Therefore, the blockage generation is investigated as a function of the operating point, the rotational speed and the inlet boundary layer thickness.

Study on the Integrated Design of Underground Construction Lighting and Ventilation System

2011 ◽  
Vol 374-377 ◽  
pp. 702-705
Author(s):  
Wei Feng ◽  
Hui Min Li
Keyword(s):  
Numerical Simulation ◽  
Thermal Environment ◽  
Ventilation System ◽  
Integrated Design ◽  
Structure Design ◽  
Light Environment ◽  
System Model ◽  
Underground Construction ◽  
New Type

In the underground building, Light environment and thermal environment is poorer, in order to improve the problem, this paper brings forward a new type of lighting and ventilation system model; discusses the principle and characteristics of transmission; and analyses the question that influences lighting and ventilated effect in the application. Structure design and numerical simulation is the focus of the next step.

Design and analysis of a propulsion mechanism using modular umbrella-like wings

2018 ◽  
Vol 122 (1249) ◽  
pp. 349-368
Author(s):  
F. Gao ◽  
J. G. Lv ◽  
X. C. Zhang
Keyword(s):  
Structural Model ◽  
Aerodynamic Force ◽  
Inertial Force ◽  
Structure Design ◽  
Symmetrical Structure ◽  
Propulsion Mechanism ◽  
New Type ◽  
Practical Guidance ◽  
Mechanical Performances ◽  
Relationship Of

ABSTRACTThis article describes the design and evaluation of a new type of propulsion mechanism that uses modular umbrella-like wings oscillating symmetrically in counterphase to generate thrust. The principle of the propulsion and movement of the modular umbrella-like wings was first developed, and the mechanism used to implement the movement of the modular wings was subsequently designed. A structural model and the assembly relationship of the propulsion mechanism were developed for prototype fabrication. An experiment was established to measure the kinematic and mechanical performances of the propulsion mechanism for different reciprocating frequencies and travels. The results for the single umbrella-like wing indicate that either increasing the frequency or enlarging the travel can enhance the average aerodynamic force generated by the wing in one cycle. The results for the modular umbrella-like wings demonstrate that the inertial force generated by the mechanism can be balanced using a symmetrical structure. The average aerodynamic force would be markedly enhanced by increasing the percentage of the time that the outspread wing is moving downwards; e.g. the average aerodynamic force generated by the modular umbrella-like wings was increased by 85.84% compared to the value for a single umbrella-like wing for the same travel and frequency. This work provides practical guidance for optimising the structure design.

Design and analysis of a new frame-foot wall-climbing robot

2021 ◽  
pp. 095440702110402
Author(s):  
Ping Huo ◽  
Yangyang Xu ◽  
Jiangtao Yu ◽  
Yazhou Wang
Keyword(s):  
Structure Design ◽  
Working Environment ◽  
Structure Stability ◽  
Foot Wall ◽  
Climbing Robot ◽  
3D Design ◽  
Motion Equations ◽  
Solution Models ◽  
New Type ◽  
The Stability

This paper designs and develops a new type of frame-foot wall-climbing robot structure. According to the bionic principle, a new parallel telescopic leg structure is proposed, and the 3D design of the overall structure of the wall-climbing robot is completed. Secondly, the kinematics analysis of the robot is carried out, and the forward and inverse solution models of the leg structure position are completed to verify the feasibility of the leg structure stability. Based on the polynomial motion equations, the robot motion planning and gait design are established, and the speed and acceleration change graphs of the leg structure slider are obtained, which avoids the rigid impact between the parts, and realizes the alternate adsorption and continuous movement of the robot legs, which the rationality of the legs structure design and the stability of the movement are verified. Through simulation and experimental results, it is shown that during the robot’s movement, the leg structure can adjust the step distance and step height according to obstacles, so as to achieve the expected obstacle crossing goal. The leg structure is adjusted according to the working environment to ensure that the fuselage and the working surface are always kept parallel to improve the stability of the overall structure.

scholarly journals Applying of depth-averaged hydrodynamic modeling with different methods of turbulence closure for flow near channel groyne. Part I – hydrodynamic background

2018 ◽  
Vol 23 ◽  
pp. 00009
Author(s):  
Ryszard Ewertowski
Keyword(s):  
Eddy Viscosity ◽  
Rectangular Channel ◽  
Simulation Models ◽  
Shear Stresses ◽  
Research Activity ◽  
Simulation Experiments ◽  
Hydrodynamic Simulation ◽  
Training Structures ◽  
Averaged Model ◽  
Bed Shear Stresses

Training structures in flow stream play an important role in shaping flow and bed properties. Planning to introduce such training elements like groins or dikes into the river stream one need to know consequences they may introduce into flow field and bed shear stresses. These consequences can be investigated by laboratory experiments on hydraulic models or by numerical modelling using hydrodynamic simulation models. In the paper the second possibility is exploited by applying two-dimensional depth-averaged model for straight rectangular channel with a groyne. This paper contains the first part of the research results and it describes hydrodynamic background of the flow phenomenon, concentrating on hydrodynamic equations for depth-averaged flow, types of eddy viscosity method used and kind of boundary conditions applied. Based on the hydrodynamic descriptions, different simulation experiments have been conducted for the flow problem and the whole analysis of simulation results for flow in channel near groyne is contained in the second part of the research activity (Part II = Analysis of simulation).

scholarly journals Aerodynamic Characteristics of Helicopter with Ducted Fan Tail Rotor in Hover under Low-Speed Crosswind

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Nahyeon Roh ◽  
Sejong Oh ◽  
Donghun Park
Keyword(s):  
Flow Characteristics ◽  
Aerodynamic Characteristics ◽  
Rotor System ◽  
Main Rotor ◽  
Complex Flow ◽  
Open Type ◽  
Low Speed ◽  
Ducted Fan ◽  
Wake Interaction ◽  
Fixed Part

The tail rotor of a helicopter operating under low-speed crosswind undergoes highly complex flow due to the interaction between the main rotor, fuselage, and tail rotor system. In this study, numerical simulations have been conducted on the complete configuration of a helicopter with a ducted fan tail rotor system (comprising a main rotor, ducted fan tail rotor, fuselage, and empennage) to analyze the wake interaction in hovering flight under various crosswind directions. The flow characteristics around the tail rotor, the tail rotor thrust, and the yawing moment of the helicopter are investigated and evaluated. The aerodynamic forces are compared with those of a helicopter with an open-type tail rotor. The results indicate that the aerodynamic performance of the ducted fan tail rotor is highly affected by the wakes of both the main rotor and port wing. Nevertheless, the helicopter with a ducted fan tail rotor is observed to be much more directionally stable under various crosswind directions, than that with an open-type tail rotor. This is because the rotor is protected by the fixed part of the tail rotor system in the former case.

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