scholarly journals NEAR-BOTTOM FLOW CHARACTERISTICS OF CURRENTS AT ARBITRARY ANGLE TO 2D RIPPLES

2011 ◽  
Vol 1 (32) ◽  
pp. 36 ◽  
Author(s):  
Ole Secher Madsen ◽  
Arlendenovega Satria Negara ◽  
Kian Yew Lim ◽  
Hin Fatt Cheong
Keyword(s):  
Current Velocity ◽  
Coastal Waters ◽  
Flow Characteristics ◽  
Velocity Profiles ◽  
Bottom Current ◽  
Arbitrary Angle ◽  
Transport Direction ◽  
Mainstream Flow ◽  
Current Flows ◽  
High Aluminum

Experimental results for near-bottom current velocity profiles for flows over artificial, definitely 2D ripples made of 1.5 cm high aluminum angle-profile spaced at 10 cm intervals are obtained for the following cases: (i) current alone perpendicular to ripples; (ii) current alone parallel to ripples; (iii) combined orthogonal wave-current flows for current parallel to ripples; and (iv) current alone at an angle of 30° to the ripple axis. The velocity profiles are analyzed by the log-profile method, and show the roughness experienced by the current to increase as the angle between ripple and current direction increases, i.e. demonstrating convincingly the reality of the concept of a direction-dependent roughness for flows over a 2D rippled bottom. Roughness experienced by the velocity component perpendicular to the ripples is, however, found to be independent of the direction of the mainstream flow relative to that of the ripples, and the different roughness experienced by the perpendicular and parallel velocity components gives rise to a turning of the current velocity vector to become increasingly aligned with the ripple crests as the bottom is approached from above. Implications of this feature, in terms of net sediment transport direction in combined wave-current flows in inner-shelf coastal waters, is discussed.

A NEW TEICHICHNOID TRACE FOSSIL SYRINGOMORPHA CYPRENSIS FROM THE MIOCENE OF CYPRUS

Palaios ◽  
2019 ◽  
Vol 34 (10) ◽  
pp. 506-514 ◽  
Author(s):  
OLMO MIGUEZ-SALAS ◽  
FRANCISCO J. RODRÍGUEZ-TOVAR ◽  
ALFRED UCHMAN
Keyword(s):  
Deep Sea ◽  
Trace Fossil ◽  
Taxonomic Group ◽  
Energy Conditions ◽  
Bottom Current ◽  
Lower Paleozoic ◽  
Shallow Marine ◽  
Current Flows

ABSTRACTA new teichichnoid trace fossil, Syringomorpha cyprensis from the Miocene of Cyprus, is proposed as a vertical burrow composed of an arcuate-like tube with horizontal parts to subhorizontal distally and vertical to subvertical parts proximally and triangular spreiten in the inner corner of the tube. Previously, this ichnogenus was represented only by the lower Paleozoic, shallow marine S. nilssoni, which disappeared after the Cambrian. Syringomorpha cyprensis marks the reappearance of similar behavior, in a deep-sea environment with pelagic, contouritic, and turbiditic sedimentation, influenced by frequent turbiditic and bottom current flows. Both ichnospecies of Syringomorpha could be produced by the same taxonomic group of probable worm like organisms (polychaetes?). Energy conditions were a stronger influence on the distribution of S. cyprensis tracemaker rather depth.

scholarly journals Experimental Study of Mean Flow Characteristics in the Near Field of Wedge-Shaped Swirling Jets

2020 ◽  
Vol 5 (10) ◽  
pp. 1199-1203
Author(s):  
Md. Mosharrof Hossain ◽  
Muhammed Hasnain Kabir Nayeem ◽  
Dr. Md Abu Taher Ali
Keyword(s):  
Flow Field ◽  
Near Field ◽  
Flow Characteristics ◽  
Velocity Profiles ◽  
Mean Flow ◽  
Mean Velocity ◽  
Potential Core ◽  
Swirling Jets ◽  
The Mean ◽  
Sinusoidal Flow

In this investigation experiment was carried out in 80 mm diameter swirling pipe jet, where swirl was generated by attaching wedge-shaped helixes in the pipe. All measurements were taken at Re 5.3e4. In the plain pipe jet the potential core was found to exist up to x/D=5 but in the swirling jet there was no existence of potential core. The mean velocity profiles were found to be influenced by the presence of wedge-shaped helixes in the pipe. The velocity profiles indicated the presence of sinusoidal flow field in the radial direction existed only in the near field of the jet. This flow field died out after x/D=3 and the existence of jet flow diminished after x/D=5.

scholarly journals Friction and mixing effects on potential vorticity for bottom current crossing a marine strait: an application to the Sicily Channel (central Mediterranean Sea)

2014 ◽  
Vol 11 (6) ◽  
pp. 2495-2532
Author(s):  
F. Falcini ◽  
E. Salusti
Keyword(s):  
Mediterranean Sea ◽  
Potential Vorticity ◽  
Eastern Mediterranean ◽  
Frictional Coefficient ◽  
Bottom Current ◽  
Topographic Effects ◽  
Central Mediterranean ◽  
Shallow Water Approximation ◽  
Sicily Channel ◽  
Current Flows

Abstract. We discuss here the evolution of vorticity and potential vorticity (PV) for a bottom current crossing a marine channel in shallow-water approximation, focusing on the effect of friction and mixing. We argue that bottom current vorticity is prone to significant sign changes and oscillations due to topographic effects when, in particular, the current flows over the sill of a channel. These vorticity variations are, however, modulated by frictional effects due to seafloor roughness and morphology. Such behavior is also reflected in the PV spatial evolution, which shows an abrupt peak around the sill region. Our theoretical findings are discussed by means of in situ hydrographic data related to the Eastern Mediterranean Deep Water, i.e., a dense, bottom water vein that flows northwestward, along the Sicily Channel (Mediterranean Sea). Indeed, the narrow sill of this channel implies that friction and entrainment need to be considered. Small tidal effects in the Sicily Channel allow for a steady theoretical approach. Our diagnoses on vorticity and PV allow us to obtain general insights about the effect of mixing and friction on the pathway and internal structure of bottom-trapped currents flowing through channels and straits, and to discuss spatial variability of the frictional coefficient. Our approach significantly differs from other PV-constant approaches previously used in studying the dynamics of bottom currents flowing through rotating channels.

Numerical, Experimental and Full-Scaled Investigation on the Current Generation System of the New Deepwater Offshore Basin

2010 ◽  
Author(s):  
Tiebing Shan ◽  
Haining Lu ◽  
Jianmin Yang ◽  
Runpei Li
Keyword(s):  
Numerical Simulation ◽  
Simulation Model ◽  
Model Test ◽  
Current Velocity ◽  
Model Tests ◽  
Constant Current ◽  
Generation System ◽  
Current Generation ◽  
The Real ◽  
Current Flows

The new deepwater offshore basin was completed in 2008 at Shanghai Jiao Tong University. The current generation system is considered to be one of the most important and challenging equipments in the basin. A lot of work has been conducted to investigate the characteristics of current generation system in the new deepwater offshore basin. Main particulars and equipments of the new basin are described in detail. Some ocean deepwater tests conducted in this new basin are also introduced. Numerical simulation, model test and full-scaled measurements in the real basin were conducted to investigate the hydraulic performances of deepwater current generation system in detail. It can be concluded that the current generation system has satisfactory performances by different methods. Uniform and constant current flows with different current velocities can be generated in this new basin. Several typical current velocity profiles can also be modeled in measuring area of the basin. It indicates that the hydraulic performances of the current generation system can satisfy requirement of offshore model tests in deepwater.

scholarly journals A numerical investigation into electroosmotic flow in microchannels with complex wavy surfaces

2011 ◽  
Vol 15 (suppl. 1) ◽  
pp. 87-94 ◽  
Author(s):  
Her-Terng Yau ◽  
Cheng-Chi Wang ◽  
Ching-Chang Cho ◽  
Cha’o-Kuang Chen
Keyword(s):  
Cross Sections ◽  
Electroosmotic Flow ◽  
Flow Characteristics ◽  
Velocity Profiles ◽  
Governing Equations ◽  
Electrical Field ◽  
Flow Recirculation ◽  
Wavy Surfaces ◽  
Pressure Driven Flow ◽  
General Method

This study investigates the flow characteristics of electroosmotic flow in a microchannel with complex wavy surfaces. A general method of coordinate transformation is used to solve the governing equations describing the electroosmotic flow in the microchannel. Numerical simulations are performed to analyze the effects of wave amplitude on the electrical field, flow streamlines, and flow fields in the microchannel. The simulation results show that, compared to a traditional pressure-driven flow, flow recirculation is not developed in the electroosmotic flow in a microchannel with complex wavy surfaces. The simulations also show that the electrical field and velocity profiles change along the channel in the region of wavy surfaces. Non-flat velocity profiles are observed in different cross-sections of the channel in the region of wavy surfaces.

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