scholarly journals LAMINAR DAMPING OF OSCILLATORY WAVES DUE TO BOTTOM FRICTION

1966 ◽  
Vol 1 (10) ◽  
pp. 10 ◽  
Author(s):  
Yuichi Iwagaki ◽  
Yoshito Tsuchiya
Keyword(s):  
Wave Amplitude ◽  
Experimental Studies ◽  
Bottom Friction ◽  
Laminar Boundary Layers ◽  
Wave Channel ◽  
Direct Measurements ◽  
Amplitude Attenuation ◽  
Side Walls ◽  
Basic Equations ◽  
Oscillatory Waves

The purpose of this paper is to discover the mechanism of the laminar damping of oscillatory waves due to bottom friction with the aid of the theory of the laminar boundary layer due to waves and of the measurements of instantaneous shearing stresses exerted on a smooth bottom, resulting from wave motion and wave amplitude attenuation with distance. In a theoretical approach the effects of convective terms involved in the basic equations of laminar boundary layers developing both on the bottom and the side walls of a wave channel, are considered on the basis of an approximate solution of the equation, and a theory of the laminar damping of Airy waves is established. In experimental studies, furthermore, direct measurements of instantaneous stresses and observations of wave amplitude attenuation were performed, and the experimental results are compared with both the above theory and the linearized one.

scholarly journals INTERACTION OF WAVES AND A TURBULENT CURRENT

1976 ◽  
Vol 1 (15) ◽  
pp. 22 ◽  
Author(s):  
J.D.A. Van Hoften ◽  
S. Karaki
Keyword(s):  
Experimental Investigation ◽  
Gravity Waves ◽  
Wave Amplitude ◽  
Current System ◽  
Bottom Shear Stress ◽  
Wave Dissipation ◽  
Wave Channel ◽  
Amplitude Attenuation ◽  
Current Interaction ◽  
The Waves

An experimental investigation was made to study wave-current interaction. Wave amplitude attenuation was measured along a laboratory wave channel to compare wave dissipation with and without flow. Mean, wave, and turbulent velocities were also measured to determine the modifications of the flow imposed by the gravity waves propogating with the current. The process of energy transfer in the wave current system was studied. Energy was found to be extracted from the waves, diffused downward and dissipated by an increase in bottom shear stress.

MELTING ABOUT A HEATED CYLINDER IN AN ICE-FILLED SQUARE ENCLOSURE WITH AN ISOTHERMALS FREE SURFACE

1999 ◽  
Vol 23 (3-4) ◽  
pp. 409-423
Author(s):  
P.H. Oosthuizen ◽  
J.T. Paul
Keyword(s):  
Free Surface ◽  
Numerical Study ◽  
Experimental Studies ◽  
Freezing Temperature ◽  
Lower Surface ◽  
Uniform Temperature ◽  
Square Enclosure ◽  
Heated Cylinder ◽  
Finite Element Procedure ◽  
Side Walls

A numerical study of the flow about and heat transfer from a heated cylinder centrally positioned in a square enclosure containing ice has been undertaken. The cylinder is heated to a uniform temperature that is higher than the freezing temperature of water and melting, therefore, occurs in the vicinity of the cylinder. The two side-walls of the enclosure are kept at a uniform temperature that is below the freezing temperature. The conditions considered here are such that there can be significant natural convection in the water near the cylinder. The lower surface of the enclosure is assumed to be adiabatic. The liquid has a free surface which is assumed to be flat. In most previous numerical studies of such a situation it has been assumed that the free surface is adiabatic. In experimental studies of the is type of flow, however, the free surface is often effectively cooled. In order to evaluate the effect of this, it has here been assumed that the free surface is at the uniform temperature that is below the freezing temperature but that is, in general, higher than that of the cooled side-walls. The governing equations have been expressed in dimensionless form and solved using a finite element procedure. The effect of the various governing parameters on the mean cylinder Nusselt number and on the thickness of the melted region about the cylinder have mainly been considered. The effect of the assumed free-surface temperature has, in particular, been studied.

scholarly journals THE SOLITARY WAVE: ITS CELERITY, PROFILE, INTERNAL VELOCITIES AND AMPLITUDE ATTENUATION IN A HORIZONTAL SMOOTH CHANNEL

2000 ◽  
Vol 1 (3) ◽  
pp. 2 ◽  
Author(s):  
James W. Daily ◽  
Samuel C. Stephan, Jr.
Keyword(s):  
Solitary Wave ◽  
Wave Height ◽  
Water Depth ◽  
Wave Length ◽  
Horizontal Displacement ◽  
Smooth Channel ◽  
Amplitude Attenuation ◽  
Oscillatory Waves

The solitary wave consists of a single elevation of water above the originally undisturbed level as shown in Figure 1. It is translatory, a passing wave causing a definite net horizontal displacement of the liquid. While the characteristics of oscillatory waves depend on wave length as well as wave height and water depth, the solitary wave is apparently described completely by the wave height and water depth so long as attenuation due to friction is unimportant.

scholarly journals Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part A (Pressure Flows)

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1488 ◽  
Author(s):  
Marschik ◽  
Dörner ◽  
Roland ◽  
Miethlinger ◽  
Schöppner ◽  
...  
Keyword(s):  
High Performance ◽  
Flow Analysis ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Polymer Melt ◽  
Wave Dispersion ◽  
Pressure Distributions ◽  
Extrusion Die ◽  
Wave Channel ◽  
Pressure Flows

Wave-dispersion screws have been used industrially in many types of extrusion processes, injection molding, and blow molding. These high-performance screws are constructed by replacing the metering section of a conventional screw with a melt-conveying zone consisting of two or more parallel flow channels that oscillate periodically in-depth over multiple cycles. With the barrier flight between the screw channels being selectively undercut, the molten resin is strategically forced to flow across the secondary flight, assuring repeated cross-channel mixing of the polymer melt. Despite the industrial relevance, very few scientific studies have investigated the flow in wave-dispersion sections in detail. As a result, current screw designs are often based on traditional trial-and-error procedures rather than on the principles of extrusion theory. This study, which was split into two parts, was carried out to systematically address this issue. The research reported here (Part A) was designed to reduce the complexity of the problem, exclusively analyzing the pressure-induced flows of polymer melts in wave sections. Ignoring the influence of the screw rotation on the conveying characteristics of the wave section, the results could be clearly assigned to the governing type of flow mechanism, thereby providing a better understanding of the underlying physics. Experimental studies were performed on a novel extrusion die equipped with a dual wave-channel system with alternating channel depth profiles. A seminumerical modeling approach based on network theory is proposed that locally describes the downchannel and cross-channel flows along the wave channels and accurately predicts the pressure distributions in the flow domain. The solutions of our seminumerical approach were, moreover, compared to the results of three-dimensional non-Newtonian CFD simulations. The results of this study will be extended to real screw designs in Part B, which will include the influence of the screw rotation in the flow analysis.

scholarly journals ANALYSIS OF STRENGTHENING OF COMPRESSED REINFORCED CONCRETE STRUCTURES USING REINFORCED CONCRETE JACKETS / GNIUŽDOMŲJŲ GELŽBETONINIŲ KONSTRUKCIJŲ STIPRINIMO GELŽBETONINIAIS APVALKALAIS ANALIZĖ

2011 ◽  
Vol 3 (2) ◽  
pp. 76-84
Author(s):  
Saulius Pilkavičius
Keyword(s):  
Reinforced Concrete ◽  
Carrying Capacity ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Calculation Methods ◽  
Advantages And Disadvantages ◽  
Calculation Algorithms ◽  
Capacity Calculation ◽  
Basic Equations ◽  
Concrete Elements

This article investigates two chosen calculation methods of compressed reinforced concrete elements strengthened using reinforced concrete jackets. Shortly describe carrying capacity calculation algorithms of these calculation methods. Present elements basic equations and dependences of carrying capacity. For calculation methods of carrying capacity comparison and adjustment executed carrying capacity experimental studies of compressed fiber reinforcement concrete elements strengthened using reinforcement concrete jackets. Were compared theoretical calculations of carrying capacity results with experimental carrying capacity results. Shortly describe advantages and disadvantages of analyzed calculation methods and experimental research. By the comparison of calculation methods conclusions and experimental studies conclusions, produces improved calculation method of carrying capacity.

Research on the Dynamic-Elegance Property of Fabric

2013 ◽  
Vol 796 ◽  
pp. 161-165
Author(s):  
Yu Ti Zhang ◽  
Dao Shun Xue ◽  
Li Na Liu
Keyword(s):  
Cluster Analysis ◽  
Wave Amplitude ◽  
Dynamic Performance ◽  
Deformation Characteristics ◽  
Testing Device ◽  
Separate Study ◽  
Bending Rigidity ◽  
Half Wave ◽  
Amplitude Attenuation ◽  
Fabric Deformation

Fabric deformation performance is an index that characterizes the dynamic performance of the fabric. However there is no separate study about fabric deformation performance. According to morphological wave data measured by fabric deformation testing device made by ourselves, we have determined to cluster analysis fabric deformation performance with the following six indicators, that is, the wavelength of the first half-wave, amplitude, half-wave area, shape coefficients, amplitude attenuation coefficient, and the number of half-wave, and also have done comparative analysis of deformation characteristics of four types of fabric. The results showed that the six indicators can measure the different kinds of fabric’s deformation characters much better, and showed that the weight of per square meter of fabrics and bending rigidity have influenced significantly. The research results have a realistic meaning for fabric processing technology and the rational use

Experimental studies of strongly stratified flow past three-dimensional orography

1999 ◽  
Vol 390 ◽  
pp. 223-249 ◽  
Author(s):  
S. B. VOSPER ◽  
I. P. CASTRO ◽  
W. H. SNYDER ◽  
S. D. MOBBS
Keyword(s):  
Flow Visualization ◽  
Froude Number ◽  
Vortex Shedding ◽  
Wave Amplitude ◽  
Wave Train ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Stratified Flow ◽  
Finite Depth ◽  
Buoyancy Frequency

Stably stratified flows past three-dimensional orography have been investigated using a stratified towing tank. Flows past idealized axisymmetric orography in which the Froude number, Fh=U/Nh (where U is the towing speed, N is the buoyancy frequency and h is the height of the obstacle) is less than unity have been studied. The orography considered consists of two sizes of hemisphere and two cones of different slope. For all the obstacles measurements show that as Fh decreases, the drag coefficient increases, reaching between 2.8 and 5.4 times the value in neutral flow (depending on obstacle shape) for Fh[les ]0.25. Local maxima and minima in the drag also occur. These are due to the finite depth of the tank and can be explained by linear gravity-wave theory. Flow visualization reveals a lee wave train downstream in which the wave amplitude is O(Fhh), the smallest wave amplitude occurring for the steepest cone. Measurements show that for all the obstacles, the dividing-streamline height, zs, is described reasonably well by the formula zs/h=1−Fh. Flow visualization and acoustic Doppler velocimeter measurements in the wake of the obstacles show that vortex shedding occurs when Fh[les ]0.4 and that the period of the vortex shedding is independent of height. Based on velocity measurements in the wake of both sizes of hemisphere (plus two additional smaller hemispheres), it is shown that a blockage-corrected Strouhal number, S2c =fL2/Uc, collapses onto a single curve when plotted against the effective Froude number, Fhc=Uc/Nh. Here, Uc is the blockage-corrected free-stream speed based on mass-flux considerations, f is the vortex shedding frequency and L2 is the obstacle width at a height zs/2. Collapse of the data is also obtained for the two different shapes of cone and for additional measurements made in the wake of triangular and rectangular at plates. Indeed, the values of S2c for all these obstacles are similar and this suggests that despite the fact that the obstacle widths vary with height, a single length scale determines the vortex-street dynamics. Experiments conducted using a splitter plate indicate that the shedding mechanism provides a major contribution to the total drag (∼25%). The addition of an upstream pointing ‘verge region’ to a hemisphere is also shown to increase the drag significantly in strongly stratified flow. Possible mechanisms for this are discussed.

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