scholarly journals Exact solution for motion of an Oldroyd-B fluid over an infinite flat plate that applies an oscillating shear stress to the fluid

2012 ◽  
Vol 2012 (1) ◽  
Author(s):  
Nazish Shahid ◽  
Mehwish Rana ◽  
Imran Siddique
Keyword(s):  
Exact Solution ◽  
Shear Stress ◽  
Flat Plate ◽  
Oscillating Shear Stress

Analysis of the Elastic Contact of a Hollow Ball With a Flat Plate

1970 ◽  
Vol 92 (1) ◽  
pp. 138-142 ◽  
Author(s):  
J. H. Rumbarger ◽  
R. C. Herrick ◽  
P. R. Eklund
Keyword(s):  
Shear Stress ◽  
Stress Field ◽  
Flat Plate ◽  
Normal Load ◽  
Thick Wall ◽  
Elastic Contact ◽  
Solid Ball ◽  
Ball Contact ◽  
Contact Life ◽  
Hollow Ball

This paper presents the analysis of the stress field in a hollow sphere in the vicinity of the contact area. The sphere is subjected to a normal load applied through a flat plate. The elastic contact shape and extent are developed for a load of 1000 lb applied to a 1-in-dia hollow ball with a 0.08-in-thick wall. Hollow ball shell bending stresses have a significant effect upon the subsurface stress field. Fatigue life estimates for the hollow ball vary significantly depending upon the selection of decisive stress amplitude. Comparison of the maximum value and location of the reversing orthogonal subsurface shear stress with solid ball data according to the Lundberg-Palmgren dynamic life theory predicts a 91.6 percent life reduction for the hollow ball contact. The use of the unidirectional subsurface shear stress results in a prediction of hollow ball contact life over 30 times the solid ball contact life.

3-D Simulation for Blood Flow and Artery Compression in Asymmetric Stenotic Arteries With Axial Stretch

2001 ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Shunnichi Kobayashi
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Shear Stress ◽  
Wall Stress ◽  
Small Strain ◽  
Rigid Wall ◽  
Severe Stenosis ◽  
Physiological Conditions ◽  
Oscillating Shear Stress ◽  
Stenotic Arteries

Abstract There has been increasing evidence that severe stenosis may cause artery compression and plaque cap rupture leading to heart attack and stroke. The physiological conditions under which that may occur and mechanisms involved are not well understood. It has been known that severe stenosis causes critical flow and wall mechanical conditions such as flow limitation, flow separation, low and oscillating shear stress distal to the stenosis, high shear stress and low or even negative flow pressure at the throat of stenosis, artery compression or even collapse. Those conditions are related to limitation of blood supply, intimal thickening and thrombosis formation, endothelism damage, platelet activation and aggregation, plaque cap rupture (for review, see [1,2]). Due to the complexity of the problem and lack of experimental data for mechanical properties of arteries under both expansion and compression, previous models were limited primarily to flow behaviors and with various limitations (axisymmetry, rigid wall, small strain, small pressure gradient). In this paper, experimental data for artery mechanical properties under physiological conditions were measured and a 3-d computational model is introduced to investigate flow behaviors and wall stress and strain distributions with fluid-structure interactions to better understand the mechanism involved in artery compression and plaque cap rupture.

scholarly journals Effects of Caveolin-1-ERK1/2 pathway on endothelial cells and smooth muscle cells under shear stress

2019 ◽  
Vol 245 (1) ◽  
pp. 21-33 ◽  
Author(s):  
Lan Jia ◽  
Lihua Wang ◽  
Fang Wei ◽  
Chen Li ◽  
Zhe Wang ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Smooth Muscle ◽  
Growth Factor ◽  
Caveolin 1 ◽  
Low Shear Stress ◽  
And Migration ◽  
Oscillating Shear Stress ◽  
Low Shear ◽  
Proliferation And Migration

Hemodynamic forces have an important role in venous intimal hyperplasia, which is the main cause of arteriovenous fistula dysfunction. Endothelial cells (ECs) constantly exposed to the shear stress of blood flow, converted the mechanical stimuli into intracellular signals, and interacted with the underlying vascular smooth muscle cells (VSMCs). Caveolin-1 is one of the important mechanoreceptors on cytomembrane, which is related to vascular abnormalities. Extracellular signal-regulated kinase1/2 (ERK1/2) pathway is involved in the process of VSMCs proliferation and migration. In the present study, we explore the effects of Caveolin-1-ERK1/2 pathway and uremia toxins on the endothelial cells and VSMCs following shear stress application. Different shear stress was simulated with a ECs/VSMCs cocultured parallel-plate flow chamber system. Low shear stress and oscillating shear stress up-regulated the expression of fibroblast growth factor-4, platelet-derived growth factor-BB, vascular endothelial growth factor-A, ERK1/2 phosphorylation in endothelial cells, and proliferation and migration of VSMCs but down-regulated the Caveolin-1 expression in endothelial cells. Uremia toxin induces the proliferation and migration of VSMCs but not in a Caveolin-1-dependent manner in the static environment. Low shear stress-induced proliferation and migration of VSMCs is inhibited by Caveolin-1 overexpression and ERK1/2 suppression. Shear stress-regulated VSMC proliferation and migration is an endothelial cells-dependent process. Low shear stress and oscillating shear stress exert atherosclerotic influences on endothelial cells and VSMCs. Low shear stress modulated proliferation and migration of VSMCs through Caveolin-1-ERK1/2 pathway, which suggested that Caveolin-1 and ERK1/2 can be used as a new therapeutic target for the treatment of arteriovenous fistula dysfunction. Impact statement Venous intimal hyperplasia is the leading cause of arteriovenous fistula (AVF) dysfunction. This article reports that shear stress-regulated vascular smooth muscle cells (VSMCs) proliferation and migration is an endothelial cell (EC)-dependent process. Low shear stress (LSS) and oscillating shear stress (OSS) exert atherosclerotic influences on the ECs and VSMCs. LSS-induced proliferation and migration of VSMCs is inhibited by Caveolin-1 overexpression and extracellular signal-regulated kinase1/2 (ERK1/2) suppression, which suggested that Caveolin-1 and ERK1/2 can be used as a new therapeutic target for the treatment of AVF dysfunction.

Turbulent Vorticity Diffusion in the Stronger Wall Jet Managed by a Flat Plate Wing in the Outer Layer

2015 ◽  
Author(s):  
Takuma Katayama ◽  
Shinsuke Mochizuki
Keyword(s):  
Shear Stress ◽  
Flat Plate ◽  
Outer Layer ◽  
Large Scale ◽  
Reynolds Shear Stress ◽  
Three Dimensional ◽  
Quantitative Relationship ◽  
Wall Jet ◽  
Mean Velocity ◽  
The Mean

The present experiment focuses on the vorticity diffusion in a stronger wall jet managed by a three-dimensional flat plate wing in the outer layer. Measurement of the fluctuating velocities and vorticity correlation has been carried out with 4-wire vorticity probe. The turbulent vorticity diffusion due to the large scale eddies in the outer layer is quantitatively examined by using the 4-wire vorticity probe. Quantitative relationship between vortex structure and Reynolds shear stress is revealed by means of directly measured experimental evidence which explains vorticity diffusion process and influence of the manipulating wing. It is expected that the three-dimensional outer layer manipulator contributes to keep convex profile of the mean velocity, namely, suppression of the turbulent diffusion and entrainment.

Oscillating shear stress mediates mesenchymal transdifferentiation of EPCs by the Kir2.1 channel

2020 ◽  
Vol 35 (10) ◽  
pp. 1473-1482 ◽  
Author(s):  
Jifeng Li ◽  
Yanting He ◽  
Hongnan Bu ◽  
Meiyue Wang ◽  
Jie Yu ◽  
...  
Keyword(s):  
Shear Stress ◽  
Oscillating Shear Stress ◽  
Kir2.1 Channel

scholarly journals Analisis Perbandingan Velocity Dan Shear Stress Perkembangan Boundary Layer Flat Plate Menggunakan Turbulent Model k – ε (Standard, Realizable, RNG)

2017 ◽  
Vol 2 (1) ◽  
pp. 27-37
Author(s):  
Setyo Hariyadi S.P.
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Flat Plate ◽  
Turbulent Model ◽  
Standard Parameter

Pengertian lapisan batas adalah daerah dimana aliran mengalami hambatan karena adanya tegangan geser yang besar pada permukaan benda, sehingga partikel-partikel fluida terpaksa berhenti pada sekitar permukaan benda karena geseran viskos. Aliran fluida sejati mana pun selalu menunjukkan adanya suatu daerah yang alirannya terhambat, yaitu dekat batas yang kecepatannya relatif terhadap batas bervariasi antara nol pada batas hingga suatu harga yang dapat diduga dari solusi aliran potensial di titik yang agak jauh dari situ. Daerah yang alirannya terhambat ini disebut lapisan batas (boundary layer) dan ketebalan lapisan batas itu sendiri dinyatakan dengan δ.Proses pembentukan lapisan batas mungkin poling baik bila divisualisasikan dengan membayangkan aliran di sepanjang sebuah pelat rata. Misalkan ada aliran seragam sebuah fluida tak dapat mampat mendekati pelat dengan kecepatan freestream. Ketika fluida mencapai tepi sebelah depan, tegangan geser yang besar terbentuk dekat dengan permukaan pelat karena partikel-partikel fluida yang tiba di situ terpaksa berhenti dan partikel-partikel yang cukup dekat dan normal terhadap plat dihambat oleh geseran viscous. Lapisan batas menebal dalam arah yang sama dengan arah aliran, akibatnya perubahan kecepatan dari nol dipermukaan pelat hingga jarak tertentu pada jarak δ semakin jauh menjadi semakin besar. Laju perubahan kecepatan tadi menentukan gradient kecepatan di permukaan plat dan karena itu tegangan gesernya juga. Studi numerik telah dilaksanakan untuk menguji kinerja aerodinamis pada plat datar dengan menggunakan beberapa turbulent model k – ε (Standard, Realizable, RNG). Kecepatan freestream yang digunakan yaitu kecepatan 10 m/s dan pada kondisi udara standard. Parameter yang dievaluasi meliputi shear stress dan profil kecepatan. Dari penelitian tersebut didapatkan bahwa dengan penggunaan turbulent model k – ε Realizable menghasilkan yang terbaik dibandingkan turbulent model yang lain.

scholarly journals Supersonic Cascade Interaction

1974 ◽  
Author(s):  
H. J. Lichtfuss ◽  
H. Starken
Keyword(s):  
Exact Solution ◽  
Supersonic Flow ◽  
Flat Plate ◽  
Constant Velocity ◽  
Flow Conditions ◽  
Inlet Flow ◽  
Flow Adjustment ◽  
Outlet Flow ◽  
Quantitative Results ◽  
Cascade Interaction

The supersonic flow adjustment between two interacting blade rows is predicted theoretically. One of both cascades may have a constant velocity in the circumferential direction. The calculation is carried out in a quasi-stationary manner. This represents an exact solution if the constant inlet and outlet flow conditions are solely under the scope of view. Admitting the above assumptions it is possible to calculate the uniform outlet flow of the first and the associated inlet flow of the second cascade as a function of the circumferential velocity. Quantitative results are presented for flat plate cascades. However, the method is not at all restricted to these simple cases.

Sliding with Cavity Formation

1987 ◽  
Vol 33 (115) ◽  
pp. 255-267 ◽  
Author(s):  
A. C. Fowler
Keyword(s):  
Exact Solution ◽  
Shear Stress ◽  
Power Law ◽  
Drainage System ◽  
Cavity Formation ◽  
Effective Pressure ◽  
Dynamic Phenomenon ◽  
Basal Shear ◽  
Tunnel System

AbstractWe present a model for the determination of a sliding law in the presence of subglacial cavitation. This law determines the basal stress at a clean ice‒bedrock interface in terms of the velocity and effective pressure. The method is based on an exact solution of the Nye—Kamb (linearly viscous) sliding problem with cavities, and uses ideas of Lliboutry (1979) to construct, via renormalization methods, an approximate law for general bedrock form. We show that, for a bedrock whose spectrum has a power‒law behaviour, one obtains a sliding law which gives the basal shear stress proportional to a power of the velocity, and to a power of the effective pressure.The effect of subglacial cavitation on the drainage system is examined, using recent ideas of Kamb. For sufficiently high velocities, drainage through a Röthlisberger tunnel system is unstable, and drainage takes place through the linked system of cavities. This leads to a reduction of the effective pressure, and by taking account of this, one can rewrite the sliding law in terms of stress and velocity only.This sliding law can be multi‒valued, and it is suggested that this underlies the dynamic phenomenon of surges.

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