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 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 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).

AN INVESTIGATION ON THE CHARACTERISTICS OF BENDING, BUCKLING AND VIBRATION OF NANOBEAMS VIA NONLOCAL BEAM THEORY

2014 ◽  
Vol 11 (06) ◽  
pp. 1350085 ◽  
Author(s):  
SOUMIA BENGUEDIAB ◽  
ABDELWAHED SEMMAH ◽  
FOUZIA LARBI CHAHT ◽  
SOUMIA MOUAZ ◽  
ABDELOUAHED TOUNSI
Keyword(s):  
Scale Effects ◽  
Constitutive Relations ◽  
Equations Of Motion ◽  
Shear Deformation Theory ◽  
Free Vibration Analysis ◽  
Beam Theory ◽  
Small Scale ◽  
Shear Stresses ◽  
Nonlocal Timoshenko Beam Theory ◽  
Walled Carbon Nanotubes

In the present study, a nonlocal hyperbolic shear deformation theory is developed for the static flexure, buckling and free vibration analysis of nanobeams using the nonlocal differential constitutive relations of Eringen. The theory, which does not require shear correction factor, accounts for both small scale effects and hyperbolic variation of shear strains and consequently shear stresses through the thickness of the nanobeam. The equations of motion are derived from Hamilton's principle. Analytical solutions for the deflection, buckling load and natural frequency are presented for a simply supported nanobeam, and the obtained results are compared with those predicted by the nonlocal Timoshenko beam theory and Reddy beam theories. Present solutions can be used for the static and dynamic analyses of single-walled carbon nanotubes.

The Rotor Dynamic Coefficients of Eccentric Mechanical Face Seals

1996 ◽  
Vol 118 (1) ◽  
pp. 215-224 ◽  
Author(s):  
J. Wileman ◽  
I. Green
Keyword(s):  
Degrees Of Freedom ◽  
Reynolds Equation ◽  
Equations Of Motion ◽  
Shear Stresses ◽  
Dynamic Coefficients ◽  
Angular Deflection ◽  
Face Seals ◽  
Radial Forces ◽  
Rotor Dynamic ◽  
Additional Coupling

The Reynolds equation is extended to include the effects of radial deflection in a seal with two flexibly mounted rotors. The resulting pressures are used to obtain the forces and moments introduced in the axial and angular modes by the inclusion of eccentricity in the analysis. The rotor dynamic coefficients relating the forces and moments in these modes to the axial and angular deflection are shown to be the same as those presented in the literature for the concentric case. Additional coefficients are obtained to express the dependence of these forces and moments upon the radial deflections and velocities. The axial force is shown to be decoupled from both the angular and radial modes, but the angular and radial modes are coupled to one another by the dependence of the tilting moments upon the radial deflections. The shear stresses acting upon the element faces are derived and used to obtain the radial forces acting upon the rotors. These forces are used to obtain rotor dynamic coefficients for the two radial degrees of freedom of each rotor. The additional rotor dynamic coefficients can be used to obtain the additional equations of motion necessary to include the radial degrees of freedom in the dynamic analysis. These coefficients introduce additional coupling between the angular and radial degrees of freedom, but the axial degrees of freedom remain decoupled.

scholarly journals Relaxation process modeling in a turbulent boundary layer with nonzero free stream turbulence

1997 ◽  
Vol 3 (3) ◽  
pp. 255-265
Author(s):  
Eugen Dyban ◽  
Ella Fridman
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Process Modeling ◽  
Free Stream ◽  
Equations Of Motion ◽  
Turbulent Shear ◽  
Shear Stresses ◽  
Free Stream Turbulence ◽  
Relaxation Effects ◽  
Averaged Equations

In order to analyze the relaxation effects in a turbulent boundary layer with zero and nonzero free stream turbulence, the Reynolds-averaged equations of motion and energy are solved. As the closure of the Reynolds-averaged equations, the transport equation for turbulent shear stresses is used. The proposed approach leads to calculation of the relaxation scales in the turbulent boundary layer with zero and nonzero free stream turbulence. Results for friction coefficients, velocity profiles, shear stresses, thickness of the boundary layer and so called “superlayer” in a flat-plate turbulent boundary layer are presented. The results obtained are in agreement with those available from the experimental data.

scholarly journals Paleotsunami Inundation of a Beach Ridge Plain: Cobble Ridge Overtopping and Interridge Valley Flooding in Seaside, Oregon, USA

2010 ◽  
Vol 2010 ◽  
pp. 1-22 ◽  
Author(s):  
Curt D. Peterson ◽  
Harry M. Jol ◽  
Tom Horning ◽  
Kenneth M. Cruikshank
Keyword(s):  
Shear Stresses ◽  
Before Present ◽  
Beach Ridge ◽  
Beach Ridges ◽  
Cobble Beach ◽  
Bed Shear Stresses ◽  
Beach Plain

The Seaside beach ridge plain was inundated by six paleotsunamis during the last ~2500 years. Large runups (adjusted >10 m in height) overtopped seawardmost cobble beach ridges (7 m elevation) at ~1.3 and ~2.6 ka before present. Smaller paleotsunami (6–8 m in height) likely entered the beach plain interior (4-5 m elevation) through the paleo-Necanicum bay mouth. The AD 1700 Cascadia paleotsunami had a modest runup (6-7 m height), yet it locally inundated to 1.5 km landward distance. Bed shear stresses (100–3,300 dyne cm−2) are estimated for paleotsunami surges (0.5–2 m depths) that flowed down slopes (0.002–0.017 gradient) on the landward side of the cobble beach ridges. Critical entrainment shear stresses of 1,130–1,260 dyne cm−2 were needed to dislodge the largest clasts (26–32 cm diameter) in paleotsunami coulees that were cut (100–200 m width) into the landward side of the cobble ridges.

scholarly journals Investigation of bed shear stresses subject to external turbulence

2003 ◽  
Vol 24 (6) ◽  
pp. 816-824 ◽  
Author(s):  
Nian-Sheng Cheng ◽  
B.Mutlu Sumer ◽  
Jørgen Fredsøe
Keyword(s):  
Shear Stresses ◽  
External Turbulence ◽  
Bed Shear Stresses

scholarly journals VESSEL WAKE INDUCED SEDIMENT MOBILITY AT EAGLE HARBOR, WASHINGTON, USA

2012 ◽  
Vol 1 (33) ◽  
pp. 58
Author(s):  
David Michalsen ◽  
Zeki Demirbilek ◽  
Okey Nwogu
Keyword(s):  
Puget Sound ◽  
Critical Shear Stress ◽  
Washington State ◽  
Shear Stresses ◽  
Difference Model ◽  
Stability Model ◽  
Sediment Mobility ◽  
Bed Stress ◽  
Passenger Ferry ◽  
Bed Shear Stresses

Eagle Harbor is a small natural harbor located in central Puget Sound on the eastern side of Bainbridge Island, Washington State, USA. Over a period of about 80 years, the harbor was severely contaminated. Approximately 28.3 hectares of the contaminated harbor were capped with dredged and upland sediments from 1993 to 2008. Recent monitoring data has concluded portions of the subtidal cap has eroded and may not be physically stable. Erosion in the vicinity of the car passenger ferry sailing line suggests the cap material may not be of sufficient size to achieve the objectives of providing a physical barrier for chemical isolation. Here, a two-dimensional finite difference model using a coupled Boussinesq-Panel method is used to investigate bed shear stresses on the existing sediment cap to analyze cap stability. Model results indicate the subtidal cap experiences over 100 Pa of bed stress within a 30 meter swath of the ferry sailing line. These bed stresses significantly exceed the critical shear stress of the original cap material indicating the cap is not physically stable.

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