Model investigation of the performance of single anchors and groups of anchors

1994 ◽  
Vol 31 (2) ◽  
pp. 273-284 ◽  
Author(s):  
Ashraf Ghaly ◽  
Adel Hanna
Keyword(s):  
Failure Mechanism ◽  
Load Distribution ◽  
Dense Medium ◽  
Unit Weight ◽  
Experimental Investigations ◽  
Experimental Setup ◽  
Uplift Capacity ◽  
Sand Surface ◽  
Pullout Load ◽  
Upward Displacement

Experimental investigations on the performance of single and groups of vertical screw anchors installed in dense, medium, and loose sands are presented. An experimental setup was instrumented to allow the measurement of the total pullout load, upward displacement, sand surface deflection, and stress development in the sand layer during all phases of testing. A sand placing technique was developed and utilized over all the testing program to ensure reproducibility of the predetermined unit weight. Stresses measured within sand deposits indicated that the tested sands were overconsolidated due to the application of mechanical compaction. Special tests were conducted on colored–layered sand to define the nature of the failure mechanism. The results of these tests, together with the measurements of the deflection of the sand surface, were employed to establish the shape of the rupture surface which could be represented by a segment of a logarithmic spiral. Groups of three, four, six, and nine anchors were tested in this investigation. The effect of installation depth, spacing between anchors, and sand characteristics on the ultimate pullout load of the group was examined. The experimental setup was instrumented to allow the measurement, of the total pullout load of the group as well as that of individual anchors in the group. Load distribution among the anchors of a group is discussed in terms of anchor location and the applied load level. At failure, all anchors contribute almost equally to the uplift capacity. Group efficiencies were calculated and compared. An installation procedure was proposed to avoid differential upward displacement during the uplifting process and to provide uniform load distribution on the different anchors of the group. Key words : anchors, failure mechanism, group action, model tests, sand, uplift capacity.

Experimental and theoretical studies on installation torque of screw anchors

1991 ◽  
Vol 28 (3) ◽  
pp. 353-364 ◽  
Author(s):  
Ashraf Ghaly ◽  
Adel Hanna
Keyword(s):  
Soil Mechanics ◽  
Testing Procedure ◽  
Dense Medium ◽  
Theoretical Studies ◽  
Uplift Capacity ◽  
Factors Affecting ◽  
Sand Surface ◽  
Pullout Load ◽  
Upward Displacement ◽  
Experimental And Theoretical Studies

Experimental and theoretical studies on the torque required to install screw anchors in sand are presented. Tests were conducted on five models of screw anchors with different geometry to study the effect of the shape of the screw element on the performance of the anchor during installation. Anchors were installed into prepared layers of dense, medium, and loose sand. An experimental setup was instrumented to allow the measurement of the total pullout load, the upward displacement, the sand surface deflection, installation torque value, and the stress development in the sand layer during all phases of the testing procedure. Special tests were conducted on coloured-layered sand to examine the effect of the installation procedure on the sand deposit and to define the sand wedge involved in resisting the installation of the screw anchor. Based on the results of the experimental investigation, the factors affecting the value of the installation torque were identified. A theoretical model was developed, from which the required installation torque value can be predicted. A torque factor was established in terms of the parameters affecting the torque value, and a correlation between this factor and the uplift capacity factor was proposed. From this correlation, the uplift capacity of a screw anchor can be determined from the measured installation torque value. A comparison between theoretical and experimental results showed good agreement. Also, reasonable agreement was observed when the present theoretical results were compared with the available field results from other investigations. Key words: anchorages, anchors, bearing capacity, helical anchors, models, sand, screw anchors, screw helical anchors, soil mechanics, torque, uplift capacity.

scholarly journals A Critical Review of Experimental Investigations about Convective Heat Transfer Characteristics of Nanofluids under Turbulent and Laminar Regimes with a Focus on the Experimental Setup

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 6004
Author(s):  
Gianpiero Colangelo ◽  
Noemi Francesca Diamante ◽  
Marco Milanese ◽  
Giuseppe Starace ◽  
Arturo de Risi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Research Field ◽  
Experimental Investigations ◽  
Experimental Setup ◽  
Increase Energy Efficiency

In this study, several experimental investigations on the effects of nanofluids on the convective heat transfer coefficient in laminar and turbulent conditions were analyzed. The aim of this work is to provide an overview of the thermal performance achieved with the use of nanofluids in various experimental systems. This review covers both forced and natural convection phenomena, with a focus on the different experimental setups used to carry out the experimental campaigns. When possible, a comparison was performed between different experimental campaigns to provide an analysis of the possible common points and differences. A significant increase in the convective heat transfer coefficient was found by using nanofluids instead of traditional heat transfer fluids, in general, even with big data dispersion from one case to another that depended on boundary conditions and the particular experimental setup. In particular, a general trend shows that once a critic value of the Reynolds number or nanoparticle concentrations is reached, the heat transfer performance of the nanofluid decreases or has no appreciable improvement. As a research field still under development, nanofluids are expected to achieve even higher performance and their use will be crucial in many industrial and civil sectors to increase energy efficiency and, thus, mitigate the environmental impact.

Experimental investigations on the failure mechanism and self-sharpening of a graded tool

2019 ◽  
Vol 23 (4) ◽  
pp. 511-529 ◽  
Author(s):  
Guangming Zheng ◽  
Xiang Cheng ◽  
Li Li ◽  
Jun Zhao ◽  
Guoyong Zhao ◽  
...  
Keyword(s):  
Failure Mechanism ◽  
Experimental Investigations

Investigation on determining uplift capacity and failure mechanism of the pile groups in sand

2020 ◽  
Vol 218 ◽  
pp. 108145
Author(s):  
Buse Emirler ◽  
Mustafa Tolun ◽  
Abdulazim Yildiz
Keyword(s):  
Failure Mechanism ◽  
Uplift Capacity ◽  
Pile Groups

Assessment of Weld Joint Efficiency for Rolled and Welded Joint for Intermediate Heat Exchanger in Sodium Cooled Fast Reactor

2014 ◽  
Vol 592-594 ◽  
pp. 1438-1442
Author(s):  
Suman Gupta ◽  
P. Chellapandi
Keyword(s):  
Heat Exchanger ◽  
Load Distribution ◽  
Welded Joint ◽  
Experimental Investigations ◽  
Tube Material ◽  
Allowable Stresses ◽  
Intermediate Heat Exchanger ◽  
Main Barrier ◽  
Maximum Stresses ◽  
Basic Strength

The tube to tubesheet joint in a heat exchanger is one of the most critical joint and it has to meet stringent requirements as it provides the main barrier between the tube side and shell side fluids of heat exchanger. This paper discusses the various kinds of tube to tubesheet joint in heat exchanger, joint configuration adopted in PFBR IHX, structural analysis of IHX, axial load distribution in tube rows and experimental verification in order to evaluate allowable strength of tube to tubesheet joint. In IHX, tubes in outer rows are under tension and maximum stresses are below the allowable stresses in the tubes. Detailed experimental investigations result shows that the rolled and welded joint is stronger than the basic strength of the tube material. However, the allowable tensile strength of the joint under mechanical loading considered is 0.95 times the allowable value for tubes as per ASME.

Experimental investigation of the uplift behaviour of circular plate anchors embedded in sand

2002 ◽  
Vol 39 (3) ◽  
pp. 648-664 ◽  
Author(s):  
K Ilamparuthi ◽  
E A Dickin ◽  
K Muthukrisnaiah
Keyword(s):  
Experimental Investigation ◽  
Circular Plate ◽  
Large Scale ◽  
Alternative Methods ◽  
Scale Model ◽  
Uplift Capacity ◽  
Rupture Surface ◽  
Sand Surface ◽  
Plate Anchors ◽  
Loose Medium

An experimental investigation of the uplift behaviour of relatively large scale model circular plate anchors up to 400 mm in diameter embedded in loose, medium-dense, and dense dry sand is described. Uplift capacity is strongly influenced by anchor diameter, embedment ratio, and sand density. In tests on shallow half-cut models, a gently curved rupture surface emerged from the top edge of the anchor to the sand surface at approximately ϕ/2 to the vertical, where ϕ is the angle of shearing resistance. For a deep anchor, a balloon-shaped rupture surface emerged at 0.8ϕ to the vertical immediately above the anchor and was confined within the sand bed. The load-displacement behaviour of full-shaped models was three-phase and two-phase for shallow and deep anchors, respectively. Alternative methods of determining the critical embedment ratio are considered, and values of 4.8, 5.9, and 6.8 are proposed for loose, medium-dense, and dense sand, respectively. Empirical equations are presented which yield breakout factors similar to those from many published laboratory and field studies.Key words: circular anchor, uplift capacity, sand, critical embedment ratio, failure mechanism.

Experimental study of the nature of the load distribution on the turns of the thread of the planetary roller-screw mechanism

2019 ◽  
Author(s):  
O.A. Ryakhovskiy ◽  
A.S. Marokhin ◽  
A.N. Vorobyev ◽  
O.A. Khachirova
Keyword(s):  
Load Distribution ◽  
Axial Load ◽  
Flat Surface ◽  
Experimental Setup ◽  
Feed Drives ◽  
The Press ◽  
Roller Screw ◽  
Screw Mechanism ◽  
Force Displacement ◽  
Made In

The article considers the effect of axial load on the turns of the thread of the planetary roller-screw converter of rotational motion into translational one. For this purpose an experimental setup was made in which the nut lies end-face on the flat surface of the press, a screw is screwed into it. The force is applied to the screw through a ball to distribute the load uniformly. The design of the machine for compression measurement allows automatic recording the axial mutual movement of tested mechanism parts when the loading force changes. Contact and displacement occur when the loading force reaches 300 N. The results are obtained in the form of a "force – displacement" graph. In the course of the experiment, the influence of step error on the uniformity of the contacts of the turns of the mating parts of the planetary roller-screw mechanism was checked. The results of the experiment are analyzed, the influence of inaccuracy of manufacturing thread of planetary roller-screw mechanism parts on its capacity for use in feed drives of various machines is considered.

Unsteady Steam Turbine Optimization Using High Fidelity CFD

2020 ◽  
Author(s):  
Vahid Iranidokht ◽  
Ilias Papagiannis ◽  
Anestis Kalfas ◽  
Reza Abhari ◽  
Shigeki Senoo ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Computational Cost ◽  
Flow Distribution ◽  
Fast Response ◽  
Test Facility ◽  
Experimental Investigations ◽  
Experimental Setup ◽  
Efficiency Gain ◽  
Flow Angle ◽  
Computational Optimization

Abstract This paper presents the computational methodology, and experimental investigations accomplished to enhance the efficiency of a turbine stage by applying non-axisymmetric profiling on the rotor hub wall. The experimental setup was a two-stage axial turbine, which was tested at “LISA” test facility at ETH Zurich. The 1st stage was considered to create the flow history for the 2nd stage, which was the target of the optimization. The hub cavity of the 2nd stage was designed with large dimensions as a requirement of a steam turbine. The goal was to optimize the interaction of the cavity leakage flow with the rotor passage flow to reduce the losses and increase efficiency. The computational optimization was completed using a Genetic Algorithm coupled with an Artificial Neural Network on the 2nd stage of the test turbine. Unsteady time-accurate simulations were performed, using in-house developed “MULTI3” solver. Besides implementing all geometrical details (such as hub and tip cavities and fully 3D blade geometries) from the experimental setup into the computational model, it was learned that the unsteady upstream effect could not be neglected. A novel approach was introduced by using unsteady inlet boundary conditions to consider the multistage effect while reducing the computational cost to half. The importance of this implementation was tested by performing a steady simulation on the optimized geometry. The predicted efficiency gain from steady simulations was 4.5 times smaller (and negligible) compared to the unsteady approach. Excluding the cavity geometry was also assessed in a different simulation setup showing 3.9% over-prediction in the absolute efficiency value. Comprehensive steady and unsteady measurements were performed utilizing pneumatic, Fast Response Aerodynamic (FRAP), and Fast Response Entropy (FENT) probes, on the baseline and profiled test cases. The end-wall profiling was found to be successful in weakening the strength of the hub passage vortex by a 19% reduction in the under-over turning. As a result, the blockage was reduced near the hub region leading to more uniform mass flow distribution along the span. The flow angle deviations at the higher span position were also corrected due to better control of the flow angles. Furthermore, the improvements were confirmed by reductions in entropy, Secondary Kinetic Energy, and pressure unsteadiness. The accurate computational implementations led to an excellent agreement between the predicted and measured efficiency gain.

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