Hydrodynamic Forces on Intermittently Spanning Pipelines in Steady Currents

2019 ◽  
Author(s):  
Yunfei Teng ◽  
Liang Cheng ◽  
Hongwei An ◽  
Feifei Tong ◽  
Terry Griffiths ◽  
...  
Keyword(s):  
Reynolds Numbers ◽  
Hydrodynamic Forces ◽  
Experimental Investigations ◽  
Hydrodynamic Drag ◽  
Hydrodynamic Behavior ◽  
Subcritical Region ◽  
Gap Ratio ◽  
The Mean ◽  
Drag And Lift ◽  
Gap Height

Abstract Experimental investigations on the hydrodynamic forces on an intermittently spanning pipeline exposed to steady currents were carried out. The effect of intermittent local spanning sections on the global hydrodynamic behavior was studied by changing the ratio between the non-spanning length (B) and the total length (L), namely the blocking ratio B / L. A range of gap height (G) to diameter (D) ratios, i.e. gap ratio G / D, and 4 different Reynolds numbers (Re) in the subcritical region were tested in the experiments. The results show: i) for a certain gap ratio, the mean drag increases gently with the decreasing blocking ratio at Re = 5.5 × 104, whereas the mean lift decreases significantly with the decreasing blocking ratio at all values of Re tested; and ii) for a certain blocking ratio, increasing the gap ratio leads to an increase in mean drag and decrease in mean lift. Further, simple approaches are proposed based on the present dataset for estimating the global effects on hydrodynamic drag and lift forces due to local spanning geometry.

Vortex-Excited Response of Large-Scale Cylinders in Sheared Flow

1988 ◽  
Vol 110 (3) ◽  
pp. 272-277 ◽  
Author(s):  
J. A. Humphries ◽  
D. H. Walker
Keyword(s):  
Large Scale ◽  
Shear Velocity ◽  
Reynolds Numbers ◽  
Hydrodynamic Drag ◽  
Flow Induced Vibration ◽  
Sheared Flow ◽  
Drag Forces ◽  
Linear Shear ◽  
Series Of Experiments ◽  
The Mean

A series of experiments were performed to measure the vortex-excited response of a 0.168-m-dia slender circular cylinder in a range of linear shear velocity profiles. Reynolds numbers of up to 2.5 × 105 were achieved. The results clearly showed that regular large-amplitude cylinder vibrations occurred well within the critical drag transition region. It was found that increasing the linear shear profile decreased the peak amplitude response but broadened the range of lock-on over which large oscillations occurred. The flow-induced vibration of the cylinder caused amplification of the mean hydrodynamic drag forces acting on the cylinder when compared with those expected for a similar rigid cylinder.

scholarly journals Convective Heat Transfer in a Rotating Cylindrical Cavity

1982 ◽  
Author(s):  
J. M. Owen ◽  
H. S. Onur
Keyword(s):  
Heat Transfer ◽  
Flow Visualization ◽  
Laser Doppler Anemometry ◽  
Reynolds Numbers ◽  
Nusselt Numbers ◽  
Gap Ratio ◽  
Wide Range ◽  
The Mean ◽  
Radial Outflow ◽  
Good Agreement

In order to gain an understanding of the conditions inside air-cooled gas-turbine rotors, flow visualization, laser-doppler anemometry and heat-transfer measurements have been made in a rotating cavity with either an axial throughflow or a radial outflow of coolant. For the axial throughflow tests, a correlation has been obtained for the mean Nusselt number in terms of the cavity gap ratio, the axial Reynolds number and rotational Grashof number. For the radial outflow tests, velocity measurements are in good agreement with solutions of the linear (laminar and turbulent) Ekman layer equations, and flow visualization has revealed the destabilizing effect of buoyancy forces on the flow structure. The mean Nusselt numbers have been correlated, for the radial outflow case, over a wide range of gap ratios, coolant flow rates, rotational Reynolds numbers and Grashof numbers. As well as the three (forced convection) regimes established from previous experiments, a fourth (free convection) regime has been identified.

Convective Heat Transfer in a Rotating Cylindrical Cavity

1983 ◽  
Vol 105 (2) ◽  
pp. 265-271 ◽  
Author(s):  
J. M. Owen ◽  
H. S. Onur
Keyword(s):  
Heat Transfer ◽  
Flow Visualization ◽  
Laser Doppler Anemometry ◽  
Reynolds Numbers ◽  
Nusselt Numbers ◽  
Gap Ratio ◽  
Wide Range ◽  
The Mean ◽  
Radial Outflow ◽  
Good Agreement

In order to gain an understanding of the conditions inside air-cooled, gas-turbine rotors, flow visualization, laser-doppler anemometry, and heat-transfer measurements have been made in a rotating cavity with either an axial throughflow or a radial outflow of coolant. For the axial throughflow tests, a correlation has been obtained for the mean Nusselt number in terms of the cavity gap ratio, the axial Reynolds number, and rotational Grashof number. For the radial outflow tests, velocity measurements are in good agreement with solutions of the linear (laminar and turbulent) Ekman layer equations, and flow visualization has revealed the destabilizing effect of buoyancy forces on the flow structure. The mean Nusselt numbers have been correlated, for the radial outflow case, over a wide range of gap ratios, coolant flow rates, rotational Reynolds numbers, and Grashof numbers. As well as the three (forced convection) regimes established from previous experiments, a fourth (free convection) regime has been identified.

Wave Induced Hydrodynamic Forces on Vertical Piggyback Risers

2002 ◽  
Author(s):  
Robert Olsen ◽  
Shan Huang
Keyword(s):  
Reynolds Numbers ◽  
Hydrodynamic Forces ◽  
Wave Forces ◽  
Close Proximity ◽  
Different Depths ◽  
Mean Water Level ◽  
Drag And Lift ◽  
Different Diameters ◽  
Vertical Cylinders ◽  
Wave Induced

The wave induced hydrodynamic forces on a pair of vertical cylinders of different diameters in close proximity are investigated experimentally. The smaller cylinder is placed at various positions around the larger one. The wave forces, including both drag and lift, are measured on each cylinder independently at two different depths below the mean water level for each cylinder. The Keulegan-Carpenter numbers vary from 0.4 to 14 based upon the larger cylinder diameter and the Reynolds numbers are in the sub-critical regime. It is found that there is significant interference effect upon the cylinder drag and inertia coefficients.

Influence of Proximity of the Seabed on Hydrodynamic Forces on a Submarine Piggyback Pipeline Under Wave Action

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Xiaofei Cheng ◽  
Yongxue Wang ◽  
Guoyu Wang
Keyword(s):  
Numerical Model ◽  
Hydrodynamic Forces ◽  
Wave Action ◽  
Experimental Investigations ◽  
Wave Forces ◽  
Equivalent Diameter ◽  
Two Dimensional ◽  
Force Coefficients ◽  
Irregular Wave ◽  
Gap Ratio

Experimental investigations were mainly carried out to clarify the influence of the seabed proximity on hydrodynamic forces on a submarine piggyback pipeline under regular and irregular wave action. Nondimensional force coefficients for drag, inertia and lift on the piggyback pipeline were obtained with an equivalent diameter based on the Morison equation. The effect of the gap ratio e/D between the bottom of the large pipeline and the seabed on force coefficients of the piggyback pipeline was studied. The results indicated that the force coefficients initially decreased and then remained constant when e/D was beyond 0.5. In addition, a two-dimensional hybrid numerical model, FEM-k-ω-VOF, was applied for a numerical analysis. A comparison of numerical and experimental results showed that the calculated values of wave forces agreed well with those of the experiments and that the numerical model can be employed to predict the hydrodynamic forces on the submarine piggyback pipeline.

scholarly journals Aerodynamics of smooth and rough square-section prisms at incidence in very high Reynolds-number cross-flows

2021 ◽  
Vol 62 (3) ◽  
Author(s):  
Nils Paul van Hinsberg
Keyword(s):  
Reynolds Number ◽  
Cross Sections ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Surface Boundary ◽  
Experimental Proof ◽  
Surface Boundary Layer ◽  
Pitch Moment ◽  
The Mean ◽  
High Reynolds

Abstract The aerodynamics of smooth and slightly rough prisms with square cross-sections and sharp edges is investigated through wind tunnel experiments. Mean and fluctuating forces, the mean pitch moment, Strouhal numbers, the mean surface pressures and the mean wake profiles in the mid-span cross-section of the prism are recorded simultaneously for Reynolds numbers between 1$$\times$$ × 10$$^{5}$$ 5 $$\le$$ ≤ Re$$_{D}$$ D $$\le$$ ≤ 1$$\times$$ × 10$$^{7}$$ 7 . For the smooth prism with $$k_s$$ k s /D = 4$$\times$$ × 10$$^{-5}$$ - 5 , tests were performed at three angles of incidence, i.e. $$\alpha$$ α = 0$$^{\circ }$$ ∘ , −22.5$$^{\circ }$$ ∘ and −45$$^{\circ }$$ ∘ , whereas only both “symmetric” angles were studied for its slightly rough counterpart with $$k_s$$ k s /D = 1$$\times$$ × 10$$^{-3}$$ - 3 . First-time experimental proof is given that, within the accuracy of the data, no significant variation with Reynolds number occurs for all mean and fluctuating aerodynamic coefficients of smooth square prisms up to Reynolds numbers as high as $$\mathcal {O}$$ O (10$$^{7}$$ 7 ). This Reynolds-number independent behaviour applies to the Strouhal number and the wake profile as well. In contrast to what is known from square prisms with rounded edges and circular cylinders, an increase in surface roughness height by a factor 25 on the current sharp-edged square prism does not lead to any notable effects on the surface boundary layer and thus on the prism’s aerodynamics. For both prisms, distinct changes in the aerostatics between the various angles of incidence are seen to take place though. Graphic abstract

scholarly journals Plunging Airfoil: Reynolds Number and Angle of Attack Effects

Aerospace ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 216
Author(s):  
Emanuel A. R. Camacho ◽  
Fernando M. S. P. Neves ◽  
André R. R. Silva ◽  
Jorge M. M. Barata
Keyword(s):  
Reynolds Number ◽  
High Performance ◽  
Angle Of Attack ◽  
Systems Design ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Low Reynolds Numbers ◽  
Operational Conditions ◽  
Naca0012 Airfoil ◽  
The Mean

Natural flight has consistently been the wellspring of many creative minds, yet recreating the propulsive systems of natural flyers is quite hard and challenging. Regarding propulsive systems design, biomimetics offers a wide variety of solutions that can be applied at low Reynolds numbers, achieving high performance and maneuverability systems. The main goal of the current work is to computationally investigate the thrust-power intricacies while operating at different Reynolds numbers, reduced frequencies, nondimensional amplitudes, and mean angles of attack of the oscillatory motion of a NACA0012 airfoil. Simulations are performed utilizing a RANS (Reynolds Averaged Navier-Stokes) approach for a Reynolds number between 8.5×103 and 3.4×104, reduced frequencies within 1 and 5, and Strouhal numbers from 0.1 to 0.4. The influence of the mean angle-of-attack is also studied in the range of 0∘ to 10∘. The outcomes show ideal operational conditions for the diverse Reynolds numbers, and results regarding thrust-power correlations and the influence of the mean angle-of-attack on the aerodynamic coefficients and the propulsive efficiency are widely explored.

Experimental investigations of flow over NACA airfoils 0021 and 4412 of wind turbine blades with and without Tubercles

2021 ◽  
pp. 0309524X2110071
Author(s):  
Usman Butt ◽  
Shafqat Hussain ◽  
Stephan Schacht ◽  
Uwe Ritschel
Keyword(s):  
Wind Tunnel ◽  
Drag Coefficient ◽  
Wind Turbine ◽  
Critical Region ◽  
Lift Coefficient ◽  
Turbine Blades ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Experimental Investigations ◽  
Wind Turbine Blades

Experimental investigations of wind turbine blades having NACA airfoils 0021 and 4412 with and without tubercles on the leading edge have been performed in a wind tunnel. It was found that the lift coefficient of the airfoil 0021 with tubercles was higher at Re = 1.2×105 and 1.69×105 in post critical region (at higher angle of attach) than airfoils without tubercles but this difference relatively diminished at higher Reynolds numbers and beyond indicating that there is no effect on the lift coefficients of airfoils with tubercles at higher Reynolds numbers whereas drag coefficient remains unchanged. It is noted that at Re = 1.69×105, the lift coefficient of airfoil without tubercles drops from 0.96 to 0.42 as the angle of attack increases from 15° to 20° which is about 56% and the corresponding values of lift coefficient for airfoil with tubercles are 0.86 and 0.7 at respective angles with18% drop.

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