Investigation on Drag Reduction Through Dimple Machining

2018 ◽  
Author(s):  
Majid TabkhPaz ◽  
Lindsay Howell ◽  
Zachary Kockerbeck ◽  
Simon Park ◽  
Ron Hugo
Keyword(s):  
Drag Reduction ◽  
Silicone Oil ◽  
Reynolds Numbers ◽  
System Capacity ◽  
Micro Milling ◽  
Fluid Viscosity ◽  
Low Reynolds Numbers ◽  
Milling Tool ◽  
Transmission Pipeline ◽  
Surface Patterns

High friction between a fluid and a pipe wall results in increased pumping requirements. This friction contributes to lower production rates and reduced system capacity. Thermal heating, fluid blending, and drag reducing agents (DRA) are commonly used methods for decreasing pressure drop in pipelines. Surface patterns inscribed onto internal pipe walls have also been shown to reduce fluid friction. In this paper, the effects of different surface patterns on the shear between a fluid and a wall are studied. Surfaces with different dimple patterns are investigated. Micro-dimpled patterns on the surface are created using an inclined, flat end micro-milling tool. The surfaces with different dimpled patterns are characterized and tested through morphological, contact angle, and viscosity measurement studies. The effects of the surface patterns are also studied through simulation. A Power Law relationship and apparent fluid viscosity is determined for the low Reynolds numbers investigated. The deepest dimpled surfaces investigated (0.2 mm dimple depth) result in a drag reduction of approximately 20% for silicone oil. Further research and application of the results to transmission pipeline systems are discussed.

scholarly journals Dynamics of viscoelastic pipe flow at low Reynolds numbers in the maximum drag reduction limit

2019 ◽  
Vol 874 ◽  
pp. 699-719 ◽  
Author(s):  
Jose M. Lopez ◽  
George H. Choueiri ◽  
Björn Hof
Keyword(s):  
Drag Reduction ◽  
Turbulent Flows ◽  
Pipe Flow ◽  
Domain Size ◽  
Reynolds Numbers ◽  
Weissenberg Number ◽  
Pipe Length ◽  
Low Reynolds Numbers ◽  
Maximum Drag Reduction ◽  
Low Reynolds

Polymer additives can substantially reduce the drag of turbulent flows and the upper limit, the so-called state of ‘maximum drag reduction’ (MDR), is to a good approximation independent of the type of polymer and solvent used. Until recently, the consensus was that, in this limit, flows are in a marginal state where only a minimal level of turbulence activity persists. Observations in direct numerical simulations at low Reynolds numbers ($Re$) using minimal sized channels appeared to support this view and reported long ‘hibernation’ periods where turbulence is marginalized. In simulations of pipe flow at $Re$ near transition we find that, indeed, with increasing Weissenberg number ($Wi$), turbulence expresses long periods of hibernation if the domain size is small. However, with increasing pipe length, the temporal hibernation continuously alters to spatio-temporal intermittency and here the flow consists of turbulent puffs surrounded by laminar flow. Moreover, upon an increase in $Wi$, the flow fully relaminarizes, in agreement with recent experiments. At even larger $Wi$, a different instability is encountered causing a drag increase towards MDR. Our findings hence link earlier minimal flow unit simulations with recent experiments and confirm that the addition of polymers initially suppresses Newtonian turbulence and leads to a reverse transition. The MDR state on the other hand results at these low$Re$ from a separate instability and the underlying dynamics corresponds to the recently proposed state of elasto-inertial turbulence.

Effects of Bio-Inspired Micro-Scale Surface Patterns on the Profile Losses in a Linear Cascade

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Qiang Liu ◽  
Shan Zhong ◽  
Lin Li
Keyword(s):  
Pressure Loss ◽  
Reynolds Numbers ◽  
Loss Reduction ◽  
Turning Angle ◽  
Low Reynolds Numbers ◽  
Linear Cascade ◽  
Micro Scale ◽  
Pressure Loss Coefficient ◽  
Surface Patterns ◽  
Scale Surface

Abstract In this paper, we investigated the effects of herringbone riblets, a type of bio-inspired micro-scale surface patterns, on pressure losses and flow turning angles in a linear cascade over a range of low Reynolds numbers from 0.50 × 105 to 1.50 × 105 and at three different incidence angles. Our experiments showed that despite their micro-scale size, herringbone riblets produced a significant reduction in pressure loss and a substantial increase in flow turning angle except at the low end of the Reynolds numbers tested. In comparison to the baseline case without riblets, the highest reduction in the zone-averaged pressure loss coefficient behind one flow passage was 36.4% which was accompanied by a 4.1 deg increase in the averaged turning angle. The loss reduction was caused by a decrease in γmax at α = −1 deg, a narrower wake zone at α = 9 deg and a mixture of both at α = 4 deg due to the suppression of flow separation on the blade suction surface. It was also noted that such a significant improvement was always accompanied by the appearance of a serrated wake structure in the contours of pressure loss coefficient in which the region with a higher loss reduction occurring directly behind the divergent region of herringbone riblets. The observed improvement in cascade performance was attributed to the secondary flow motion produced by herringbone riblets which energizes the boundary layer. Overall, this work has produced convincing experimental evidence that herringbone riblets could be potentially used as passive flow control devices for reducing flow separation in compressors at low Reynolds numbers.

scholarly journals An energy-efficient pathway to turbulent drag reduction

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ivan Marusic ◽  
Dileep Chandran ◽  
Amirreza Rouhi ◽  
Matt K. Fu ◽  
David Wine ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Drag Reduction ◽  
Large Scale ◽  
Reynolds Numbers ◽  
Small Scale ◽  
Power Cost ◽  
Turbulent Fluid Flow ◽  
Low Reynolds Numbers ◽  
Turbulent Drag ◽  
Direct Measurements

AbstractSimulations and experiments at low Reynolds numbers have suggested that skin-friction drag generated by turbulent fluid flow over a surface can be decreased by oscillatory motion in the surface, with the amount of drag reduction predicted to decline with increasing Reynolds number. Here, we report direct measurements of substantial drag reduction achieved by using spanwise surface oscillations at high friction Reynolds numbers ($${{{\mathrm{Re}}}_{\tau }}$$ Re τ ) up to 12,800. The drag reduction occurs via two distinct physical pathways. The first pathway, as studied previously, involves actuating the surface at frequencies comparable to those of the small-scale eddies that dominate turbulence near the surface. We show that this strategy leads to drag reduction levels up to 25% at $${{{{{{{{\mathrm{Re}}}}}}}}}_{\tau }$$ Re τ = 6,000, but with a power cost that exceeds any drag-reduction savings. The second pathway is new, and it involves actuation at frequencies comparable to those of the large-scale eddies farther from the surface. This alternate pathway produces drag reduction of 13% at $${{{{{{{{\mathrm{Re}}}}}}}}}_{\tau }$$ Re τ = 12,800. It requires significantly less power and the drag reduction grows with Reynolds number, thereby opening up potential new avenues for reducing fuel consumption by transport vehicles and increasing power generation by wind turbines.

Swimming in Crustacea

1985 ◽  
Vol 76 (2-3) ◽  
pp. 115-122 ◽  
Author(s):  
Robert R. Hessler
Keyword(s):  
Drag Reduction ◽  
Reynolds Numbers ◽  
Power Stroke ◽  
Relative Area ◽  
Common Occurrence ◽  
Low Reynolds Numbers ◽  
Recovery Stroke ◽  
Low Reynolds ◽  
Basic Motion

ABSTRACTAn analysis of swimming in living crustaceans is presented in order to elucidate the range of ways this function has been achieved, and to reveal the principles which constrain it. The study focuses on Gnathophausia ingens, a primitive, bathypelagic malacostracan that swims with thoracic exopods and pleopods. These structures consist of a muscular peduncle and one or two flagella that are fringed with setulate setae. The basic motion is rowing with the limb and setal fan extended on the power stroke and flexed on recovery.A survey of other crustaceans shows that rowing with this type of swimming structure dominates throughout, although paddles often replace the flagella. Particularly pervasive is the large relative area of setae, whose effectiveness must stem from the ability to extend and flex passively and from the high drag generated on the power stroke by the setules at low Reynolds numbers.A review of reconstructions of Palaeozoic trilobites and marrellomorphs reveals the likelihood that if swimming was the function of the exites, they operated inefficiently or were employed in other methods as well. Sculling and drag reduction on the recovery stroke through feathering rather than flexion are possible alternatives. The more common occurrence of paddle-like limb shafts and blade-like marginal structures in other Palaeozoic arthropods is also noted.

An experimental study on the behaviours of circular synthetic jets at low Reynolds numbers

2012 ◽  
Vol 226 (11) ◽  
pp. 2686-2700 ◽  
Author(s):  
Qingfeng Xia ◽  
Shan Zhong
Keyword(s):  
Reynolds Number ◽  
Silicone Oil ◽  
Reynolds Numbers ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Operating Conditions ◽  
Flow Visualisation ◽  
Stroke Length ◽  
Low Reynolds Numbers ◽  
Low Reynolds

In the work presented in this article, the behaviour of circular synthetic jets issuing into quiescent surrounding fluid at low Reynolds numbers is experimentally studied for potential mixing applications of synthetic jets at micro-scales or in highly viscous fluids. Sugar solutions and silicone oil are used as the flow media in order to achieve the required low Reynolds numbers. The conditions for jet instability, vortex rollup and synthetic jet formation are investigated using both flow visualisation techniques and particle image velocimetry, and the typical behaviour of synthetic jets at a Reynolds number around unity is also illustrated. The roles of Reynolds number, dimensionless stroke length and Stokes number in determining the characteristics of synthetic jets are examined and found to be largely consistent with the finding obtained at higher Reynolds numbers. Finally, a parameter map of synthetic jet flow patterns is produced based on the results from this study, which can be used to aid the choice of synthetic jet operating conditions for specific applications or anticipate if a desired vortex structure can be obtained at a given synthetic jet operating condition.

scholarly journals Relaminarization of wall turbulence by high-pressure ramps at low Reynolds numbers

2016 ◽  
Vol 20 (suppl. 1) ◽  
pp. 93-102 ◽  
Author(s):  
Kwonyul Song ◽  
Jovan Jovanovic ◽  
Ahmed Al-Salaymeh ◽  
Cornelia Rauh ◽  
Antonio Delgado
Keyword(s):  
High Pressure ◽  
Pipe Flow ◽  
Silicone Oil ◽  
Reynolds Numbers ◽  
Wall Turbulence ◽  
Working Fluid ◽  
Hot Wire ◽  
Low Reynolds Numbers ◽  
Reverse Transition ◽  
Low Reynolds

Reverse transition from the turbulent towards the laminar flow regime was investigated experimentally by progressively increasing the pressure up to 400 MPa in a fully developed pipe flow operated with silicone oil as the working fluid. Using hot-wire anemometry, it is shown indirectly that at low Reynolds numbers a rapid increase in pressure modifies the turbulence dynamics owing to the processes which induce the effects caused by fluid compressibility in the region very close to the wall. The experimental results confirm that under such circumstances, the traditional mechanism responsible for self-maintenance of turbulence in wall-bounded flows is altered in such a way as to lead towards a state in which turbulence cannot persist any longer.

Airfoil Deterministic Lateral Displacement for High-Throughput Particle Separation in Viscous Fluids

2020 ◽  
Author(s):  
Brian Senf ◽  
Kawkab Ahasan ◽  
Jong-Hoon Kim
Keyword(s):  
High Throughput ◽  
Biological Sample ◽  
Particle Trajectory ◽  
Lateral Displacement ◽  
Particle Separation ◽  
Reynolds Numbers ◽  
Deionized Water ◽  
Fluid Viscosity ◽  
Deterministic Lateral Displacement ◽  
Low Reynolds Numbers

Abstract Deterministic Lateral Displacement (DLD) is an inertial size-based particle separation technique with great possibilities for use with biological sample preparation. Recently it has been shown that particle shift of a DLD is highly dependent on the Reynolds number. Additionally, particle trajectory has been characterized in a high throughput airfoil array DLD with varying Angle of Attack (AoA) in Deionized water. The AoA can be shifted negatively assisting in particle trajectory increases at low Reynolds numbers. With variations in fluid viscosity, particle trajectories compared to Reynolds value should theoretically have a constant and similar slope. In this work, various viscosities are tested in a DLD with a neutral and negative AoA to eventually characterize non-Newtonian fluids within a DLD. Due to higher viscosities increasing the internal pressure of the device, the negative AoA DLD shows promising results at higher range viscosities due to its ability to shift particles at lower Reynolds numbers.

Sign in / Sign up

Export Citation Format

Share Document