Percentage Drag Reduction Research Articles

Uticaj međuaerodiska sa montiranim oštrim šiljastim vrhom na smanjenje otpora po površini poluloptastog tela pri Mahovom broju 2.0

Reduction of forebody drag in high speed flying vehicles such as rockets and missiles are of high research interest in the present time. In the present research, drag reduction obtained by using an intermediate aerodisk mounted sharp tip spike has been investigated using computational studies at Mach number of 2.0. The flowfield over a hemispherical blunt body with an intermediate aerodisk mounted sharp tip spike is investigated at zero degree angle of attack and the amount of drag reduction obtained is then compared with that of a conventional sharp tip spike mounted hemisphere. The presence of an intermediate aerodisk changes the flow physics and shock system over the blunt body. The change in the system of shock waves by mounting an intermediate aerodisk results in a higher percentage (20% higher) of drag reduction generated by the blunt spiked body moving at a supersonic speed of Mach 2.0. Use of intermediate aerodisk proves to be beneficial in terms of drag reduction for spike lengths ranging beyond the critical length.

Active Flow Control of Flapping Airfoil Using Openfoam

ABSTRACTThe concept of the fixed wing Micro Air Vehicles (MAVs) has received increasing interest over the past few decades, with the principal aim of carrying out the surveillance missions. The design of the flapping wing MAVs still is in infancy stage. On the other hand, there has been increasing interest over the flow control using plasma actuators in worldwide. The aim of this research is to study the flow control of a flapping airfoil with and without plasma actuation in OpenFOAM. The OpenFOAM CFD platform has been used to develop our own plasma solver. For the plasma induced turbulence in the flow regime, k-ε turbulence model was adopted to address the interaction between plasma and fluid flows. For the plasma-fluid interaction, we use reduced-order modelling to solve the plasma induced electric force. A two dimensional NACA0012 flapping airfoil without plasma actuation study has been benchmarked with previous published literature. We have not only focused on the active flow control but also analyzed the important parameter reduced frequency at different values, those are 0.1, 0.05 and 0.025. Reduced frequency (κ) is very important parameter of an airfoil in the unsteady motion. Our major contribution is testing the several reduced frequencies with the plasma actuation. The positive and beneficial effects of the plasma actuator for all cases have been observed. From the observed results, the flapping with plasma actuation at reduced frequency of 0.1 showed the 14.285 percent lift improvement and the 16.19 percent drag reduction than the flapping without plasma actuation at the respective dynamic stall angles. The maximum lift coefficient is increased with the increase in reduced frequency. In overall, plasma actuators are effective in the flow control of a flapping airfoil. In future, the combination of the flapping with plasma actuators will be a promising application to boast the maneuverability of MAVs.

Observation on the drag reducing effect of low concentration chitosan solution in turbulent pipe flow

Polymer-based drag reducing agent (DRA) is used widely in various industries due to its ability to enhance fluid flow as well as economically beneficial to various sectors. This study is conducted to observe the drag reducing effect of chitosan as DRA and observed its effect on the turbulent flow inside the pipe. The experiment is conducted in a closed loop circulation system where water is the transport medium. The pipe system consist of acrylic pipes with 0.013 m, 0.025 m and 0.038 m diameter. The chitosan was extracted from shrimp shells and five different concentration of chitosan were tested. The degree of deacetylation of the chitosan shows 97% which indicates its solubility in water. It was found that the highest drag reduction percentage were obtained from 0.038 m pipe of 33 ppm concentration which is 28%. The flow pattern inside the pipe is also analysed and discussed in this study

IMPROVEMENT OF SHARARA CRUDE OIL FLOW USING POLYSTYRENE AND POLYDIMETHYLSILOXANE AS DRAG REDUCING AGENTS

In this study the applicability of the Libyan crude oil flow induced by improved lab pumping system was examined in order to evaluate the effect of adding polymeric materials of Polystyrene and Polydimethylsiloxane as drag reducing agents (DRA) on the flow of Sharara crude oil in the pipeline. The polymers are injected through a pumping system at different concentrations rounded between (10-100) ppm. Several experiments were carried out to determine the best concentration of polymer, which satisfied lowest drag force on of crude oil flow rate. Furthermore, the effect of additive concentration on the Viscosity(μ), friction factor (ƒ), percentage drag reduction (%DR) and the amount of flow increases (%FI) were determined. The results show that the activities of Polydimethylsiloxane for Drag reduction is higher than drag reduction for Polystyrene. However, the %DR is generally increased with increasing of polymer concentration for all tested additives. It is progressively increased with increasing Reynolds number (Re) at any specific concentration of the polymeric additives. The friction factor is well correlated with Reynolds numbers and polymer concentration according to the relation of the form ƒ= k ReaCb, the results showed good agreement between the observed values and the predicted ones.

MATHEMATICAL MODEL TO INVESTIGATE THE DRAG REDUCTION OF KEROSENE WITH POLYMER UNDER TURBULENT FLOW

This paper present a mathematical study on drag reduction by polymer additive suchas poly isobutylene (PIB) with kerosene in turbulent pipe flow by using computational fluiddynamic commercial package program (COMSOL 4.4) solution. Theoretically thecomputational study was used to calculate the pressure drop in two dimensions geometricmodel with 6m length and 80 mm width as a diameter of the pipe, Geometric shape has beendrawing by tools of the program windows, and to simulated the flow region mathematicallythe flow region is divide into very small parts (mesh generation). The model that used in themathematical modelling method was (k-?( mathematical turbulent model to study theinternal pipe flow properties. The continuity and momentum equations and two k-? modelequations have been solved by the program to obtain the theoretical results. There variablesthat used in the theoretical study were effective density, effective viscosity, inlet velocity,and outlet pressure. The boundary condition was inlet and outlet velocity, temperature, andpressure of flow, and the velocity (u=0) at the pipe wall. The theoretical calculations showthat the velocity and drag reduction percentage increases with polymer concentration andvolume flow rate increasing where maximum DR% is 15.8% at volume flow rate 500 ??minwith polymer concentration 100 ppm, pressure drop decreases with polymer concentrationincreasing. Friction factor decreases with polymer concentration increased, also shear stressdecrease with polymer concentration increasing.

Drag Reduction of Non-Circular Cylinder at Subcritical Reynolds Numbers

Experimental and numerical investigation of fore body geometrical effects on drag and flow-field of non-circular cylinder ( D-shaped bluff body) were conducted in the subcritical flow regime at Reynolds number in the range of 1 x 105 ≤ Re ≤ 1.8 x 105. To shield the non circular cylinder ( D-shaped model ) front surface from the positive pressure of the unsteady vortex generation in the near wake, circular disk of various geometries were attached upstream of the non-circular cylinder base model. The fore body makes the streamlines that separate from its edges to attach smoothly onto the front face shoulders of the main body, thereby converting the bluff body into an equivalent streamlined body to result in low drag. The diameter of the fore body (b1) ranges from 0.25 to 0.75 times the hydraulic diameter of base model ( b2 ) and the gap ratio ( g/ b2 ),was in the range from 0.25 to 1.75 b2. The experimental and numerical investigations show that by using a circular disk as fore body with a width ratio b1/b2 of 0.75 and a gap ratio of g/ b2 = 0.75 results in a configuration having percentage drag reduction of about 67 % and 65 % respectively.

An experimental investigation of heterogeneous injection of biopolymer (guar gum) on the flow patterns and drag reduction percentage for two phase (water-oil mixture) flow

An experimental investigation of the effect of a water-soluble biopolymer (guar gum) in horizontal water-oil flow was studied. A horizontal pipe flow facility having inner diameter 19.5 mm and length 3050 mm was used. Laboratory scale experiments were conducted using the biopolymer, which showed a positive effect on drag reduction. A master solution having 1000 ppm concentration was injected in the boundary layer by using peristaltic pump to achieve 10–50 ppm concentration. Simultaneously, effect of the drag reducing polymer on the flow patterns were investigated from stratified region to dispersed flow region. It was found that addition of the polymer in the boundary layer extended the stratified region to higher mixture velocities from lower mixture velocities. Similar experiments were performed by varying oil fraction as well as polymer concentration in the test facility. A maximum drag reduction of 50% was observed when 50 ppm polymer was injected to 0.1 oil fraction solution.

Experimental study on optimum concentration of polyacrylamide for drag reduction and heat transfer performance in a compact heat exchanger

The effects of adding polyacrylamide (PAM) to pure water on pressure drop and heat transfer in a compact heat exchanger was experimentally investigated. Laminar flow was studied to transfer heat between water and air. By adding PAM to water, the pressure drop has continuously decreased until the concentrations of 100 ppm. After this optimum concentration, the pressure drop began to increase. The maximum percentage of drag reduction (%DR) was 14%. On the other hand, the overall heat transfer coefficient decreased with the increase in PAM concentration. In this condition, the overall heat transfer coefficient had reduced by 28%.

Formation, stability and comparison of water/oil emulsion using gum arabic and guar gum and effect of aging of polymers on drag reduction percentage in water/oil flow

In this study, formation and stability of the water/oil emulsion using gum arabic and guar gum and their effect on percentage of drag reduction has been studied. Two different master solutions of emulsions were prepared by using both the polymers and their stability and degradation were studied with number of days. The concentration of gum arabic was varied from 1000 to 5000 ppm, while guar gum concentration was varied from 500 to 3000 ppm in master solution. It was found that guar gum was more stable as compared to gum arabic even with less concentration. A similar study was done by forming hydrogel using guar gum which showed only 3% degradation after 15 days as compared to gum arabic with 50% degradation. Microstructure was observed using optical microscopy and average droplet size was measured for a better understanding of the stability and morphology of oil droplets in polymer solution.

Parametric Study on Formation Flying Effectiveness for a Blended-Wing UAV

This paper investigates aerodynamic performance improvements of formation flight at transonic speeds for a medium size Unmanned Aerial Vehicle (UAV). The metric for assessing the aerodynamic improvement of formation flight is the computed drag. The total drag for each formation configuration is compared with a single UAV, where a final drag reduction percentage is estimated. The evaluation of the aerodynamic performance is conducted by employing an in-house Computational Fluid Dynamics (CFD) solver, grid generation and post processing tools. For critical understanding of the tendency of the formation efficiency depending on main parameters, broad formation configurations are analysed. The parameterisation includes number of aircraft, proximity and formation shape. Full realisation of the benefit predicted would need to be proven in the real world, but there is sufficient confidence to suggest that it exist: the empirical parametric analysis suggests that formation flight can improves aerodynamic performance and formation configuration greatly influence the degree of improvement.

Experimental and Numerical Buckling Analysis for Zig-Zag Model Composite Materials of Clamed-Clamped Rectangular Plates

flow, where adding certain amount of drag reducing agent, such as polymer. From addition of that agent, it causes a dramatic frictional drag reduction. This work shows the effect of the pressure drop on a drag reduction along pipe in a horizontal placing with kerosene flow is investigated. The tested fluid was kerosene and poly isobutylene polymer (PIB) with 50 ppm (part per million), 75 ppm, and 100 ppm weight concentration of polymer: Experimental investigation gives more description of this phenomenon. The experimental results illustrate that pressure drop and pressure gradient decreases with increasing of polymer concentration and volume flow rate. The friction factor decreases with increasing of additive concentration and velocity. The drag reduction percentage increases with increasing the mean velocity, polymer concentration and temperature. The experimental results show that maximum drag reduction (DR %) about 19%.

Experimental Investigation of Drag Reduction with polymer of Kerosene flow in a horizontal pipe

flow, where adding certain amount of drag reducing agent, such as polymer. From addition of that agent, it causes a dramatic frictional drag reduction. This work shows the effect of the pressure drop on a drag reduction along pipe in a horizontal placing with kerosene flow is investigated. The tested fluid was kerosene and poly isobutylene polymer (PIB) with 50 ppm (part per million), 75 ppm, and 100 ppm weight concentration of polymer: Experimental investigation gives more description of this phenomenon. The experimental results illustrate that pressure drop and pressure gradient decreases with increasing of polymer concentration and volume flow rate. The friction factor decreases with increasing of additive concentration and velocity. The drag reduction percentage increases with increasing the mean velocity, polymer concentration and temperature. The experimental results show that maximum drag reduction (DR %) about 19%.

Application of naturally extracted surfactant from Madhuca longifolia to improve the flow properties of heavy crude oil through horizontal pipeline

Madhuca longifolia or Mahua is a natural alternative of surfactants and cleaners. Having enormous applications in cleaning industries and its potential biodegradability, the surfactant extracted from Mahua was used as flow improver for transportation of heavy crude oil through pipeline. The beneficial effects of the surfactant on improvement of pressure drop, drag reduction and head loss for flow of crude oil has been investigated at different operating conditions through a horizontal pipeline of diameter 1.5 inch. The results showed significant influence of surfactant on the pressure drop and percentage of drag reduction. Heating of crude from 25 °C to 40 °C reduced pressure drop from 10.6 psi to 4.3 psi at a flow rate of 60 L/min whereas addition of 2000 ppm surfactant at 25 °C reduced the pressure drop to 2.6 psi at same flow rate. At same temperature, the head loss decreased from 6.77 L/min to 4.88 L/min when 2000 ppm surfactant was added to the crude oil. It was also noticed that viscosity reduction at 25 °C after addition of 2000 ppm surfactant was even greater than heating the crude to 40 °C. This can immensely serve the purpose of pipeline transportation of heavy crude oil where viscosity is a major issue. The experimental results were compared with existing models like Cross, Carreau and Krieger & Dougherty model and the crude oil was found to follow Krieger-Dougherty model. Considering the effectiveness of the surfactant, biodegradability and cost effectiveness, this novel surfactant can be used as a flow improver for crude oil during transportation through pipelines even at low temperatures.

Study of oil‐soluble and water‐soluble drag reducing polymers in multiphase flows

AbstractMultiphase flow industrial applications require reduced frictional pressure drop (drag) and lower operating costs. Drag reducing polymers (DRPs), which do not require additional infrastructure, meet this requirement. Therefore, this study investigated the effects of water‐soluble polar ZETAG® 8165 and nonpolar oil‐soluble polyisobutylene (PIB) DRPs on pressure gradient and percentage drag reduction using two‐phase air‐water and air‐oil flows, and three‐phase air‐oil‐water flow. The conduit comprised a 22.5 mm I.D. and 2.48 m long horizontal pipe. The fluid flow pattern and DRP shear stability were also studied. The functional mechanism of DRP, not adequately addressed in the literature, was especially revisited. This work suggests that the resultant interaction between the DRP state and the external environment dictates its ability for dampening turbulent eddies, streamlining the velocity field, and eventually increasing the thickness of the laminar sublayer. The DRP state includes its chemical structure and hydrodynamic size. On the other hand, the external environment comprises fluid flow pattern, polarity, phase morphology, and intensity of turbulence. Hence, the functional mode of a DRP is more involved than what the literature usually reports. ZETAG® 8165, having longer branches and ion‐pairs around the backbone, showed less shear degradation than the fairly straight‐chain PIB. The effects of these structural differences were also well‐reflected in their varying abilities to transpose flow pattern, and reduce drag and pressure gradient. For a given DRP, the air flow rate promoted or demoted the DRP performance, depending on the experimental design.

Effect of polymer and fiber additives on pressure drop in a rectangular channel

The influence of minute amounts of additives on pressure drop is an interesting fundamental phenomenon, potentially with important practical applications. Change of the pressure drop in a quasi-two-dimensional channel flow using various additives is experimentally investigated. Tests were conducted for a wide range of concentrations (100 ppm–500 ppm) and Reynolds numbers (16 000– 36 000) with two polymers and four rigid fibers used as additive. Maximum drag reduction of 22% was observed for xanthan gum. However, xanthan gum loses its drag-reducing property rapidly. It was also seen that drag reduction percentage of xanthan gum remains almost constant for different Reynolds numbers. Guar flour demonstrated good drag reduction property at high Reynolds numbers. Drag reduction of 17.5% at Re =33 200 using 300 ppm solution was observed. However, at low Reynolds numbers guar flour will cause an increase in pressure drop. Fiber fillers (aspect ratio=21) have been tested as well. In contrast to polymers, they increased the drag for the range of examined concentrations and Reynolds numbers. Polyacrylonitrile fiber with three different aspect ratios (106, 200, 400) was also used, which showed an increase in pressure drop at low aspect ratios. Polyacrylonitrile fibers of larger lengths (6 mm) demonstrated minor drag-reducing effects (up to 3%).

Parametric study of a viscoelastic RANS turbulence model in the fully developed channel flow

One of the newest of viscoelastic RANS turbulence models for drag reducing channel flow with polymer additives is studied in different flow and rheological properties. In this model, finitely extensible nonlinear elastic-Peterlin (FENE-P) constitutive model is used to describe the viscoelastic effect of polymer solution and turbulence model is developed in the k-ϵ-(ν^2 ) -f framework. The geometry in this study is two-dimensional channel flow and finite volume method (FVM) with a non-uniform collocated mesh is used to solve the momentum and constitutive equations. In order to evaluate this turbulence model, several cases with different parameters such as Reynolds numbers, Weissenberg number, maximum polymer extensibility and concentration of polymer are simulated and assessed against direct numerical simulation (DNS) data. The velocity profiles, shear stress profiles and the percentage of friction drag reduction predicted by this turbulence model are in good agreement with DNS data at moderate to high Reynolds numbers. However, in low Reynolds numbers, the results of model are reliable only for low 〖 L〗^2 value. Moreover, in case of high concentration of polymer, the accuracy of the model is lost.

Aerothermodynamic considerations for energy deposition based drag reduction technique

Numerical investigations are carried out for understanding the real gas effects for energy deposition based drag reduction technique for hypersonic flow over a blunt body. Computations are performed to compare the effectiveness of this active drag reduction technique using perfect, frozen and non-equilibrium gas flow models. It has been noticed that the deposited energy gets utilized more effectively in case of perfect gas flow. A loss up to 15% is observed in percentage drag reduction as a consequence of real gas effects over the range of energies considered herein. At low levels of deposited energies, drag predicted for frozen and non-equilibrium flows agrees well; however differences are observed at higher energy levels. It is concluded that thermal non-equilibrium plays a dominant role at low energy levels and chemical non-equilibrium at higher energy levels. The study is further extended to see the effect of energy density and free stream total enthalpy. A significant reduction (up to 74%) in power effectiveness is noticed as the total enthalpy of free stream increased. The present studies also revealed that requirement of non dimensional energy for attaining peak power effectiveness has close match at different stagnation enthalpies.

Preparation of Nano-Scale Biopolymer Extracted from Coconut Residue and Its Performance as Drag Reducing Agent (DRA)

Drag or frictional force is defined as force that acts opposite to the object’s relative motion through a fluid which then will cause frictional pressure loss in the pipeline. Drag Reducing Agent (DRA) is used to solve this issue and most of the DRAs are synthetic polymers but has some environmental issues. Therefore for this study, biopolymer known as Coconut Residue (CR) is selected as the candidate to replace synthetic polymers DRA. The objective of this study is to evaluate the effectiveness of Nano-scale biopolymer DRA on the application of water injection system. Carboxymethyl cellulose (CMC) is extracted by synthesizing the cellulose extracted from CR under the alkali-catalyzed reaction using monochloroacetic acid. The synthesize process is held in controlled condition whereby the concentration of NaOH is kept at 60%wt, 60 °C temperature and the reaction time is 4 hours. For every 25 g of dried CR used, the mass of synthesized CMC yield is at an average of 23.8 g. The synthesized CMC is then grinded in controlled parameters using the ball milling machine to get the Nano-scale size. The particle size obtained from this is 43.32 Nm which is in range of Nano size. This study proved that Nano-size CMC has higher percentage of drag reduction (%DR) and flow increase (%FI) if compared to normal-size CMC when tested in high and low flow rate; 44% to 48% increase in %DR and %FI when tested in low flow rate, and 16% to 18% increase in %DR and %FI when tested in high flow rate. The success of this research shows that Nano-scale DRA can be considered to be used to have better performance in reducing drag.

AN EXPERIMENTAL INVESTIGATION FOR WATER FLOW ENHANCEMENT IN HORIZONTAL PIPES BY USING NANOPARTICLES

This work has been devoted to investigate experimentally, the increase in range of horizontal discharge distance and velocity of water flow for pipes of fire-hoses and water jet propulsion systems in small ships. The enhancement method of water flow depends on increase the drag reduction and best uniform flow. One of the important practice techniques is adding a small amount of some materials, cheap and locally available added into water flow in a horizontal pipe.A simple experimental system is designed and constructed to investigate the increase in drag reduction. Nanoparticles (aluminum oxide –30 nm diameters) and polyacrylamide (PAM) have been added alone and gain time together. Experimental calculations of average flow velocity, Reynolds number, and friction factor and percentage drag reduction are experimentally calculated under water heads of 75,100, 125,150,175 and 200 cm.The effects of concentration ratios of nanofluid(AL2O3) on friction factor and drag reduction are studied and calculated. The present results showed that addition of AL2O3 and PAM are caused reducing in friction factor, increase in range of horizontal discharge distance and the velocity of water flow.Also the results indicated that, drag reduction was26% increased at addition of AL2O3 and 39% at PAM while at mixing them together was 52 % as average for six heads were chosen. The results are represented graphically to explain the degrees of enhancement of increasing in drag reduction, flow velocity and the range of discharge distance for water in horizontal pipes. The originality of this work was addition materials of nanopartcles with polyacrylamide together.

Computational Fluid Dynamic Simulation on NACA 0026 Airfoil with V-Groove Riblets

The aims of this research is to look into the percentage drag reduction on a NACA 0026 airfoil with V-Groove riblets installed around at some locations around its surface. NACA 0026 is a symmetrical airfoil mostly used as turbine blade and aircraft wing. Research on drag reduction by using riblets on the surface was introduced by NASA Langley Research Centre in 1970s. There are many types of riblet designed in this research area such as V groove, segmented blade and continuous sawtooth. This research used NACA 0026 with external geometry 500 mm spans, 615 mm chord and 156 mm thickness. V-groove riblets with 1 mm pitch and 1 mm high and 30 mm width are attached at peak points of the airfoil profile. The CFD simulation used ANSYS Fluent to analyze the velocity, pressure gradient, turbulent kinetic energy and vortex development. The result shows the percentage in drag reduction compared to clean surface for the zero angle of attack is 11.8% and 30 0 angle of attack is 1.64%. By this condition the airfoil will have better motion performance in their applications.