G0500305 Simulation of fresh concrete flow by Elasto-viscoplastic model : Determination of property parameters for numerical analysis

2015 ◽  
Vol 2015 (0) ◽  
pp. _G0500305--_G0500305-
Author(s):  
Tomohiro NAKAMURA
Keyword(s):  
Numerical Analysis ◽  
Fresh Concrete ◽  
Viscoplastic Model ◽  
Model Determination ◽  
Concrete Flow

Numerical Modelling of Multiphase Flow With Application to Industrial Processes

2021 ◽  
Author(s):  
◽  
Ashutosh Bhokare
Keyword(s):  
Numerical Modelling ◽  
Multiphase Flow ◽  
Multiphase Flows ◽  
Oil And Gas ◽  
Fresh Concrete ◽  
Industrial Applications ◽  
Fluidised Bed ◽  
Bingham Model ◽  
Drag Models ◽  
Concrete Flow

Multiphase flows are witnessed often in nature and the industry. Simulating the behaviour of multiphase flows is of importance to scientists and engineers for better prediction of phenomena and design of products. This thesis aims to develop a multiphase flow framework which can be applied to industrial applications such as placement of concrete in construction and proppant transport in oil and gas. Techniques available in literature to model multiphase flows are systematically introduced and each of their merits and demerits are analysed. Their suitability for different applications and scenarios are established. The challenges surrounding the placement of fresh concrete in formwork is investigated. Construction defects, the physics behind these defects and existing tests used to monitor fresh concrete quality are evaluated. Methods used to simulate fresh concrete flow as an alternative to experiments are critically analysed. The potential benefits of using numerical modelling and the shortcoming of the existing approaches are established. It is found that the homogeneous Bingham model is currently the most widely used technique to model fresh concrete flow. Determining the Bingham parameters for a given concrete mix remains a challenge and a novel method to obtain values for them is demonstrated in this work. The Bingham model is also applied to a full-scale tremie concrete placement procedure in a pile. Knowledge on the flow pattern followed by concrete being placed using a tremie is extracted. This is used to answer questions which the industry currently demands. The need for a more sophisticated model is emphasised in order to obtain an even greater understanding of fresh concrete flow behaviour. A CFD-DEM framework in which the multiphase nature of concrete is captured is developed. To validate this framework a new benchmark test is proposed in conjunction with the fluidised bed experiment. A comparative study of the drag models used in CFD-DEM approaches is performed to systematically assess each of their performances. CFD-DEM modelling is then applied to model fresh concrete flow and its potential to model defect causing phenomena is demonstrated. A model to capture more complex behaviours of concrete such as thixotropy is introduced and demonstrated.

Acceptable Dislocation of Bearings of the Turbine Set Considering Permissible Vibration and Load of the Bearings

2005 ◽  
Vol 293-294 ◽  
pp. 433-440 ◽  
Author(s):  
Jozef Rybczynski
Keyword(s):  
Numerical Analysis ◽  
Vertical Direction ◽  
Large Power ◽  
Power Turbine ◽  
Bearing Load ◽  
Bearing Vibration

The paper presents the procedure and the results of determination of acceptable dislocation for particular bearings of the large power turbine set. The ranges have been evaluated by numerical analysis of the turbine set model. Acceptable dislocations of the bearings were calculated in horizontal and vertical direction separately in regard to criterion of permissible bearing vibration and in regard to permissible bearing load. The results have been presented graphically in the form of areas of acceptable dislocations, which allow the comparison considering both criteria. The paper contains exemplary trajectory graphs for all bearings corresponding to maximum acceptable dislocations. The investigations revealed asymmetry of areas of acceptable dislocations, which suggests that the constructional kinetostatic line of rotors is not optimal.

Numerical Analysis of Cavitation Inception and Desinence Behind Orifices

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
E. L. Amromin
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Separated Flow ◽  
Computational Procedure ◽  
Cavitation Number ◽  
Laminar Flows ◽  
Cavity Pressure ◽  
Cavitation Inception ◽  
Separation Zones

Abstract Experimental results and trends for cavitation inception and desinence behind orifices in microchannels are quite different from the data obtained during previous experiments in much larger facilities. The objective of this paper is to explain these differences via a numerical analysis. The employed computational procedure is divided into two parts. The first part is computation of an axisymmetric separated flow around the orifice. The second part is determination of characteristics of cavities appearing within separation zones. The provided analysis of the experimental data of other researchers pointed out two sources of the above-mentioned differences. First, for larger orifices, the cavities appear in the cores of drifting vortices. For such a situation, cavitation inception and desinence number increases with the inflow speed due to an impact of turbulence, but there is no such an increase for microbubbles with laminar flows. Second, because of the difficulty to measure the cavity pressure in microbubbles, cavitation number is usually defined with employment of the vapor pressure, and this leads to misinterpretation of the measurements and their trends.

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