scholarly journals Validation of a two-layer depth-averaged model by comparison with an experimental dilute stratified pyroclastic density current

2021 ◽  
Vol 83 (11) ◽  
Author(s):  
Hiroyuki A. Shimizu ◽  
Takehiro Koyaguchi ◽  
Yujiro J. Suzuki ◽  
Ermanno Brosch ◽  
Gert Lube ◽  
...  
Keyword(s):  
Large Scale ◽  
Suspended Load ◽  
Numerical Results ◽  
Bed Load ◽  
Density Currents ◽  
Layer Depth ◽  
Particle Volume ◽  
Volume Fractions ◽  
Settling Speed ◽  
Averaged Model

AbstractNumerical results of a two-layer depth-averaged model of pyroclastic density currents (PDCs) were compared with an experimental PDC generated at the international eruption simulator facility (the Pyroclastic flow Eruption Large-scale Experiment (PELE)) to establish a minimal dynamical model of PDCs with stratification of particle concentrations. In the present two-layer model, the stratification in PDCs is modeled as a voluminous suspended-load layer with low particle volume fractions ($$\lesssim {10}^{-3})$$ ≲ 10 - 3 ) and a thin basal bed-load layer with higher particle volume fractions ($$\sim {10}^{-2}$$ ∼ 10 - 2 ) on the basis of the source condition in the experiment. Numerical results for the suspended load quantitatively reproduce the time evolutions of the front position and flow thickness in the experimental PDC. The numerical results of the bed-load and deposit thicknesses depend on an assumed value of settling speed at the bottom of the bed load ($${W}_{\mathrm{sH}}$$ W sH ). We show that the thicknesses of bed load and deposit in the simulations agree well with the experimental data, when $${W}_{\mathrm{sH}}$$ W sH is set to about $$1.25\times {10}^{-2}$$ 1.25 × 10 - 2 m/s. This value of the settling speed is two orders of magnitude smaller than that predicted by a hindered-settling model. The small value of $${W}_{\mathrm{sH}}$$ W sH is considered to result from decreasing in the effective deposition speed due to the erosion process accompanied by saltating/rolling of particles at the bottom of the bed load.

scholarly journals Validation of a two-layer depth-averaged model by comparison with an experimental dilute stratified pyroclastic density current

2021 ◽  
Author(s):  
Hiroyuki A. Shimizu ◽  
Takehiro Koyaguchi ◽  
Yujiro J. Suzuki ◽  
Ermanno Brosch ◽  
Gert Lube ◽  
...  
Keyword(s):  
Large Scale ◽  
Numerical Results ◽  
Density Currents ◽  
Layer Depth ◽  
Particle Volume ◽  
Hindered Settling ◽  
Volume Fractions ◽  
High Particle ◽  
Suspension Layer ◽  
Averaged Model

Abstract Numerical results of a two-layer depth-averaged model of pyroclastic density currents (PDCs) were compared with an experimental PDC generated at the international eruption simulator facility (the Pyroclastic flow Eruption Large-scale Experiment; PELE) to establish a minimal dynamical model of PDCs with stratification of particle concentrations. In the present two-layer model, the stratification in PDCs is modeled as a voluminous dilute turbulent suspension layer with low particle volume fractions (<10-2) and a thin basal bedload layer with high particle volume fractions (~10-2) on the basis of the source condition in the experiment. Numerical results for the dilute layer quantitatively reproduce the time evolutions of the front position and body thickness of the dilute part in the experimental PDC. The numerical results of the bedload thickness and deposit mass depend on an assumed value of mean deposition speed at the bottom of the bedload (D). We show that the thicknesses of bedload and deposit in the simulations agree well with the experimental data, when D is set to about 3.5 x 10-4 m/s. This value of the deposition speed is two orders of magnitude smaller than that predicted by a hindered-settling model. The small value of D suggests that the erosion process accompanied by saltating/rolling of particles plays a role in the sedimentation in the bedload.

Technical solutions envisaged in managing solids in combined sewer networks

1996 ◽  
Vol 33 (9) ◽  
pp. 237-244 ◽  
Author(s):  
Ghassan Chebbo ◽  
Dominique Laplace ◽  
André Bachoc ◽  
Yves Sanchez ◽  
Benoit Le Guennec
Keyword(s):  
Large Scale ◽  
Suspended Solids ◽  
Drainage Area ◽  
Bed Load ◽  
Urban Drainage ◽  
Combined Sewer ◽  
Wet Weather ◽  
Technical Solutions ◽  
Dry Weather Flow ◽  
Sewer Networks

Solids in combined sewer networks represent two important technical questions: - the clogging of man-entry sewers, and - pollution in urban wet weather discharges, whose main vectors are generally suspended solids. In this paper, we shall present first, curative technical solutions which avoid or remove deposits in man-entry sewers. We shall discuss the partial extraction of the largest solids; selective trapping of bed load solids, which form deposits; and the displacement of deposits using dry weather flow flushing waves. We shall then examine technical solutions to control pollution in urban wet weather discharges. This will show that decantation is an efficient means of fighting pollution. However, it is not always feasible because it involves large scale investments. Complementary methods should, therefore, be developed and used at different points in the water's passage through an urban drainage area.

Wear Behavior of In Situ Mg2Si Particle-Dispersed Magnesium Alloys

2017 ◽  
Vol 909 ◽  
pp. 100-105
Author(s):  
Kazunori Asano
Keyword(s):  
Magnesium Alloys ◽  
High Speed ◽  
Wear Behavior ◽  
Particle Dispersion ◽  
Dry Sliding Wear ◽  
Wear Loss ◽  
Mg2si Particle ◽  
Particle Volume ◽  
Volume Fractions

Magnesium alloys, in which the in-situ Mg2Si particles were dispersed, were fabricated by a casting process, and the dry sliding wear behavior of the alloys was investigated. Optical microscopy revealed that the polygonal Mg2Si particles were homogeneously dispersed in the alloys. Mg2Si particle volume fractions in the alloys were 7 and 11 vol%. Although the wear loss of the alloy decreased due to the particle-dispersion, there was no difference in the wear loss between the alloys with different volume fractions. The worn surfaces of the particle-dispersed alloys were covered with the crumbled Mg2Si particles, which would prevent seizure between the alloy and the steel counterpart, leading to an improvement in the wear resistance of the alloy. The particle-dispersion slightly decreased the scatter of the coefficient of friction during the wear for the low sliding speed and load, but the effect of the dispersion was not clearly observed for the high speed and load.

The Influence of Multiple Inclusions on the Cauchy Stress of a Spherical Particle-Reinforced Composite Under Uniaxial Loading

2014 ◽  
Author(s):  
Ke Niu ◽  
Armin Abedini ◽  
Zengtao Chen
Keyword(s):  
Spherical Particle ◽  
Single Particle ◽  
Volume Fraction ◽  
Unit Cell ◽  
Spherical Particles ◽  
Uniaxial Tensile ◽  
Cauchy Stress ◽  
Particle Volume ◽  
Volume Fractions ◽  
Unit Cells

This paper investigates the influence of multiple inclusions on the Cauchy stress of a spherical particle-reinforced metal matrix composite (MMC) under uniaxial tensile loading condition. The approach of three-dimensional cubic multi-particle unit cell is used to investigate the 15 non-overlapping identical spherical particles which are randomly distributed in the unit cell. The coordinates of the center of each particle are calculated by using the Random Sequential Adsorption algorithm (RSA) to ensure its periodicity. The models with reinforcement volume fractions of 10%, 15%, 20% and 25% are evaluated by using the finite element method. The behaviour of Cauchy stress for each model is analyzed at a far-field strain of 5%. For each reinforcement volume fraction, four models with different particle spatial distributions are evaluated and averaged to achieve a more accurate result. At the same time, single-particle unit cell and analytical model were developed. The stress-strain curves of multi-particle unit cells are compared with single-particle unit cells and the tangent homogenization model coupled with the Mori-Tanaka method. Only little scatters were found between unit cells with the same particle volume fractions. Multi-particle unit cells predict higher response than single particle unit cells. As the volume fraction of reinforcements increases, the Cauchy stress of MMCs increases.

Numerical Investigation of Local Scour Around Submerged Pipeline in Shoaling Conditions

2018 ◽  
Author(s):  
Ming-ming Liu ◽  
Ming Zhao ◽  
Lin Lu
Keyword(s):  
Water Waves ◽  
Slope Angle ◽  
Suspended Load ◽  
Local Scour ◽  
Navier Stokes ◽  
Bed Load ◽  
Scour Depth ◽  
Two Dimensional ◽  
Sediment Mass ◽  
Subsea Pipelines

Water waves play an important role in local scour around subsea pipelines laid on the sandy seabed, especially in shallow water regions. In this paper, a two-dimensional numerical model is employed to predict local scour around submarine pipelines under water waves in shoaling condition. The motion of water under waves is simulated by solving the Reynolds Averaged Navier-Stokes (RANS) equations. The evolution of the seabed surface near the pipeline is predicted by solving the conservation of the sediment mass, which transport in the water in the forms of bed load and suspended load. The main aim of this study is to investigate the effect of the seabed slope on the scour profiles and scour depth. To achieve this aim, numerical simulations of scour around a pipeline on a flat seabed and on a slope seabed with a slope angle of 15° are conducted for various wave conditions.

scholarly journals Regression analysis between sediment transport rates and stream discharge for the Nestos River, Greece

2013 ◽  
Vol 14 (3) ◽  
pp. 362-370
Keyword(s):  
Sediment Transport ◽  
Suspended Load ◽  
Bed Load ◽  
Regression Curve ◽  
Degree Polynomial ◽  
Stream Discharge ◽  
Nestos River ◽  
Polynomial Curve ◽  
Load Transport ◽  
Bed Load Transport

Systematic measurements of sediment transport rates and water discharge were conducted in the Nestos River (Greece), at a place located between the outlet of Nestos River basin and the river delta. This basin area is about 838 km2 and lies downstream of the Platanovrysi Dam. Separate measurements of bed load transport and suspended load transport were performed at certain cross sections of the Nestos River. In this study, relationships between sediment transport rates and stream discharge for the Nestos River are presented. A nonlinear regression curve (4th degree polynomial curve; r2 equals 0.62) between bed load transport rates and stream discharge, on the basis of 63 measurements, was developed. In addition, a nonlinear regression curve (5th degree polynomial curve; r2 equals 0.95) between suspended load transport rates and stream discharge, on the basis of 65 measurements, was developed. The relatively high r2 values indicate that both bed load transport rates and, especially, suspended load transport rates can be predicted as a function of the stream discharge in the Nestos River. However, the reliability of the regression equations would have been higher if more measured data were available.

scholarly journals ANALISIS SEDIMENTASI PADA BENDUNG BERINGEN SILA DESA STOWE BERANG KECAMATAN UTAN KABUPATEN SUMBAWA

2018 ◽  
Author(s):  
Badaruddin ◽  
Tri Satriawansyah ◽  
Faturrahman
Keyword(s):  
Economic Cooperation ◽  
Suspended Load ◽  
Bed Load

Bendung Beringin Sila merupakan salah satu bendung yang dibangun dengan biaya bantuan dari luar negeri yaitu Overseas Economic Cooperation Fund (OECF) – Jepang, yang berlokasi di desa Stowe Brang Kecamatan Utan Kabupaten Sumbawa yang digunakan sebagai sarana irigasi untuk mengairi areal persawahan seluas 2.400 ha. Melihat kondisi saat ini, Bendung Beringin Sila mengalami penumpukan sedimen di hulu bendung yang menutupi mercu bendung, bahkan saat banjir sekalipun sedimen dapat terlihat. Tujuan penelitian ini untuk mengetahui besarnya sedimentasi tahunan serta mengetahui besar perbandingan sedimen dasar (Bed Load) dengan sedimen melayang (Suspended Load).Untuk menghitung besar debit aliran sungai pada Sub Daerah Aliran Sungai (DAS), digunakan persamaan dasar manning yang pengaruhi oleh data curah hujan dari satu stasiun selama 5 tahun terakhir. Kemudian diuji menggunakan metode Log Person Tipe III. Serta menghitung curah hujan dan debit banjir.Besarnya sedimentasi permukaan pada Sub Daerah Aliran Sungai (DAS) Utan, digunakan persamaan dasar yang dikenal dengan rumus Schoklitsch dan Forchemeir digunakan untuk menganalisa Sedimen Dasar (Bed Load) dan Sedimen Melayang (Suspended Load) yang masuk ke Bendung Beringin Sila.Berdasarkan hasil analisa diperoleh besar Sedimen Dasar (QSD) pada saat debit normal sebesar 635712,105 ton/tahun, dan Sedimen Melayang (QSM) sebesar 1052356,320 ton/tahun, sedangkan pada saat banjir maksimum (Qr) Sedimen Dasar (Bed Load) sebesar 635712,105 ton/tahun dan Sedimen Melayang (Suspended Load) sebesar 4001918,400 ton/tahun.

scholarly journals Analisa Angkutan Sedimen Pada Hulu Bendung Aepodu Kabupaten Konawe Selatan

2021 ◽  
Vol 2 (1) ◽  
pp. 1-7
Author(s):  
Ramadhan Hidayat Putra ◽  
Amad Syarif Syukri ◽  
Catrin Sudarjat ◽  
Vickky Anggara Ilham
Keyword(s):  
Sediment Transport ◽  
River Flow ◽  
Suspended Load ◽  
Bedload Transport ◽  
Bed Load ◽  
Average Flow ◽  
Load Transport ◽  
Bed Load Transport ◽  
Transport Analysis

Research on Aepodu Weir Sediment Transport Analysis in South Konawe District, based on observations in the field, Aepodu Weir hasa sediment buildup that has now exceeded the height of the weirlight house. The purpose of the study was to analyze the magnitudeof Aepodu river flow and to analyze the amount of sedimenttransport that occurred in the Aepodu dam. The method used todetermine the amount of bed load transport uses stchoklitscht, whilefor transporting suspended load using forcheimer.The results of the analysis of the average flow of the Aepodu riverwere 3,604 m3/ second. Sediment transport that occurs in Aepoduweir is Bedload transport (Qb) of 291625.771 tons / year, andsuspended load transport (Qs) of 16972,423 tons / year, so that thetotal sediment transport (QT) is 308598,194 tons / year.

scholarly journals An efficient three-term conjugate gradient-type algorithm for monotone nonlinear equations

2020 ◽  
Author(s):  
Jamilu Sabi'u ◽  
Abdullah Shah
Keyword(s):  
Global Convergence ◽  
Nonlinear Equations ◽  
Conjugate Gradient ◽  
Large Scale ◽  
Numerical Results ◽  
Search Direction ◽  
Projection Technique ◽  
Type Algorithm ◽  
Gradient Type

In this article, we proposed two Conjugate Gradient (CG) parameters using the modified Dai-{L}iao condition and the descent three-term CG search direction. Both parameters are incorporated with the projection technique for solving large-scale monotone nonlinear equations. Using the Lipschitz and monotone assumptions, the global convergence of methods has been proved. Finally, numerical results are provided to illustrate the robustness of the proposed methods.

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