Drag Factors Research Articles

Interaction forces between pipelines and submarine slides — A geotechnical viewpoint

Assessment of interaction forces between deep water pipelines and potential submarine slides, debris flows and turbidity currents is an important aspect of geohazard studies. Historically, interaction forces have tended to be expressed in terms of drag factors, within a traditional fluid mechanics framework, with the drag factors depending strongly on an equivalent Reynolds number for the non-Newtonian debris material. Here, we have followed a more geotechnical approach, allowing the interaction forces to be expressed in terms of a strain-rate dependent shear strength of the debris material, and with the inclusion of a drag term (with fixed drag coefficient) for high velocity, low strength, combinations. This superposition approach treats separately the interaction forces that arise from the strain-rate dependent strength and the inertia of the debris, rather than combining them into a single drag force. A failure envelope is proposed, allowing axial and normal interaction forces to be estimated for any angle of attack of the debris flow.

Thirty criteria-based assessment of agility in a pneumatic enabling products manufacturing company

During the recent years, competition is intensified due to the globalisation and entry of several players in markets. This situation has facilitated the modern customers to demand innovative products and models in varied volumes. In order to fulfil this customer demand, it is necessary for the traditional manufacturing companies to practice agile manufacturing (AM) principles. On adoption of AM, a traditional company can exhibit agility by which it reacts quickly to meet the customers’ dynamic demands. AM has to be implemented by the traditional manufacturing companies by acquiring several criteria. Some of them may not exist or may exist feebly in traditional manufacturing companies. In this situation, the traditional manufacturing companies need to assess the level at which agility is practiced. In order to fulfil this need, a 30 criteria AM assessment tool is contributed in this paper. Using this tool, the total agility level in a pneumatic enabling products manufacturing company was assessed. After a comprehensive analysis, the drag and failure factors that prevent this company from becoming agile were identified. Subsequently, the mitigating actions and success ingredients for suppressing and overcoming them were evolved and suggested as proposals. Most of these proposals were acceptable to the management of this company.

Velocity profile of interplanetary coronal mass ejections beyond 1 AU

[1] We analyze the dynamics of interplanetary coronal mass ejections (ICMEs) through the interplanetary medium from the lower solar corona to ∼5.3 AU. Our analysis uses a one-dimensional hydrodynamical model derived from the fluid equation of motion that considers an effective drag force under both the laminar and turbulent hypotheses (low and high Reynolds number, respectively). The model has three sets of input parameters. The first set is related to the ICME itself, i. e., initial speed and mass; the second set of parameters is related to the ambient solar wind: density and velocity; and the final set corresponds to the ambient solar wind–ICME interaction: an ICME expansion factor and a viscosity or drag parameter. We use this model to explain the radial dynamics of a particular ICME detected at three different locations: close to the Sun, where the ICME was ejected on 20 January 2004, and detected by the SOHO/LASCO coronagraphs; two days later, at Earth's L1 by the ACE spacecraft (∼1.0 AU), and finally, ∼14 days later, at ∼5.3 AU by the Ulysses spacecraft near Jupiter's orbit. The model is then compared to a general set of ICMEs data from Ulysses that cover distances from ∼1.3 AU to ∼5.3 AU. Our model successfully reproduces the dynamical behavior of ICMEs at distances near Earth's orbit and works reasonably well at larger distances ≈5.3 AU. Therefore, our analysis shows that the ICME - solar wind interaction may be treated as a drag interaction with the appropriate drag factors, not only at distances ≤1 AU, but at larger distances. Finally, we show that our model is useful in identifying ICMEs at different heliocentric distances.

Investigation of drag effect using the field signature method

The potential drop (PD) method is an established non-destructive evaluation (NDE) technique. The monitoring of internal corrosion, erosion and cracks in piping systems, based on electrical field mapping or direct current potential drop array, is also known as the field signature method (FSM). The FSM has been applied in the field of submarine pipe monitoring and land-based oil and gas transmission pipes and containers. In the experimental studies, to detect and calculate the degree of pipe corrosion, the FSM analyses the relationships between the electrical resistance and pipe thickness using an electrode matrix. The relevant drag effect or trans-resistance will cause a large margin of error in the application of resistance arrays. It is the first time that the drag effect in the paper is investigated and analysed in resistance networks with the help of the FSM. Subsequently, a method to calculate the drag factors and eliminate its errors is proposed and presented. Theoretical analysis, simulation and experimental results show that the measurement accuracy can be improved by eliminating the errors caused by the drag effect.

Comparing National Innovation Systems in Japan and the United States: Push, Pull, Drag and Jump Factors in the Development of New Technology

What jump-starts technology commercialization, venture capital investment, and new firm formation in new technology industries? What are the most effective ways to encourage start-ups and to connect fledgling firms to critical resources? National policies targeting life science (for example, biotechnology and medical devices) in Japan and the USA are compared in the context of their national innovation systems (NIS) supporting (and hindering) new technology-based entrepreneurship as a whole. Japan has embarked on an unprecedented bet on the future potential of life science, investing nationally and locally in building up R&D and commercialization infrastructure and stimulating new business creation through its Cluster Initiative and other policies. At the same time, while the USA until now has been at the forefront in new technology entrepreneurship, national policy is currently faltering. Through an analysis of best practices in national and regional innovation systems one can get a sense of important push (for example, policy stimuli), pull (market demand), drag (capital and institutional weaknesses) and jump (targeted community-level strategies) factors underlying the ability of certain locales and countries to create competitive advantages in new technology industries.

Assessment of missile hazards: Evaluation of the fragment number and drag factors

An approach was proposed for the assessment of the expected number and drag factor of fragments generated in the collapse of a vessel due to internal pressure. The analysis of a database reporting data on more than 140 vessel fragmentation events allowed the identification of a limited number of fragment reference shapes. The correlation of fragment reference shapes to the vessel credible fragmentation patterns allowed the assessment of the expected number and reference shape of fragments generated. Starting from the fragment reference shapes identified, simplified functions for drag factor calculation were developed, based on few geometrical parameters of the vessel undergoing the fragmentation event. The probabilistic models for the expected shape and number of fragments generated and the simplified drag factor functions developed may constitute an important input for the analysis of the possible fragment trajectories in the framework of missile hazard assessment.

On avalanche measurements at the Norwegian full-scale test-site Ryggfonn

Avalanche measurements and observations, which were carried out at the Ryggfonn test-site, Norway, on 16 April 2005, are analyzed. The data include pulsed Doppler radar measurements, impact pressure readings from load cells mounted at two locations within the track and stress readings from load plates flush with the upstream slope of a catching dam. The radar measurements are used to deduce velocities and estimates on the retarding accelerations. The retarding accelerations show a wide discrepancy with commonly used model assumptions. Pressure measurements were correlated with velocity measurements. The measurements infer that commonly used drag factors are not sufficient to describe the forces exerted by slow moving wet snow. These measurements also depict transitions in the flow behavior. Measurements with load plates imply plastic failure rather than Coulomb-type friction. Field observations of the avalanche track suggest that erosion/abrasion due to (saltating) particles is one possible entrainment mechanism.

Effects of Drag Factor on Physiological Aspects of Rowing

This study examined the effects of two resistances, or "drag factors" on selected physiological variables during incremental progressive rowing tests (seven 3-min stages) on a Concept2 ergometer. Subjects were seven male and seven female university club rowers. Their mean age, body mass and height were 19.6 +/- 1.5 years, 72.7 +/- 8.0 kg, and 172.2 +/- 7.5 cm, respectively. Progressive tests were conducted using drag factors 100 (D100) and 150 (D150) before the spring racing season. Values were determined for the following physiological variables: ventilation (V.E), oxygen uptake (V.O2), heart rate (HR), blood lactate concentration (BLC), respiratory exchange ratio (R) and rowing economy (W/V.O2). Comparisons across all six submaximal stages showed no significant difference between D(100) and D(150) for any of the variables measured (p > .05). Maximal V.E(max) was significantly greater at D100 than D150 (p < .02). Maximal V.O(2), HR, BLC, R, stroke rate (SR) and W/V.O2 were greater at D100 than at D150, though not significantly so. The mean D100-D150 differences in V.E and SR for each stage were significantly correlated (r = 0.76, p < .01), suggesting drag factor may affect V.E via SR.

Variable Property and Temperature Ratio Effects on Nusselt Numbers in a Rectangular Channel With 45 Deg Angled Rib Turbulators

Measured local and spatially-averaged Nusselt numbers and friction factors (all time-averaged) are presented which show the effects of temperature ratio and variable properties in a rectangular channel with rib turbulators, and an aspect ratio of 4. The ratio of air inlet stagnation temperature to local surface temperature Toi/Tw varies from 0.66 to 0.95, and Reynolds numbers based on channel height range from 10,000 to 83,700. The square cross-section ribs are placed on two opposite surfaces, and are oriented at angles of +45 deg and −45 deg, respectively, with respect to the bulk flow direction. The ratio of rib height to channel hydraulic diameter is 0.078, the rib pitch-to-height ratio is 10, and the ribs block 25 percent of the channel cross-sectional area. Ratios of globally-averaged rib Nusselt numbers to baseline, constant property Nusselt numbers, Nu̿/Nuo,cp, increase from 2.69 to 3.10 as the temperature ratio Toi/Tw decreases from 0.95 to 0.66 (provided Reynolds number ReH is approximately constant). Friction factor ratios f/fo,cp then decrease as Toi/Tw decreases over this same range of values. In each case, a correlation equation is given which matches the measured global variations. Such global changes are a result of local Nusselt number ratio increases with temperature ratio, which are especially pronounced on the flat surfaces just upstream and just downstream of individual ribs. Thermal performance parameters are also given, which are somewhat lower in the ribbed channel than in channels with dimples and/or protrusions mostly because of higher rib form drag and friction factors.

Heat Transfer in a Channel with Dimples and Protrusions on Opposite Walls

Local and spatially averaged Nusselt-number data are presented forthe dimpled surface of a channel, both with and without protrusions (with the same shapes as the dimples ) on the opposite wall. Channel aspect ratio is 16, ratio of channel height to dimple print diameter is 0.5, Reynolds numbers based on channel height ranges from 5 ££ 10 3 to 3:5 ££ 10 4 , and ratio of channel inlet stagnation temperature to wall temperature ranges from 0.73 to 0.94. Because of the added vortical, secondary e ow structures and e ow unsteadiness induced by the protrusions, local and spatially averaged Nusselt numbers are augmented considerably and have greater Reynolds-number dependence, compared to a channel with a smooth top wall and dimples on one opposite wall. Nusselt-number variations arealso observed asthelocation ofthearray of protrusionsis changed with respect to thedimples. Form drag and channel friction factors are augmented, and thermal performance factors are then generally lower when protrusions are employed, compared to a channel with a smooth top surface and a dimpled bottom surface. Nomenclature D = dimple print diameter f = channel friction factor f0 = baseline friction factor in channel measured with smooth top and bottom channel surfaces H = channel height k = thermal conductivity Nu = Nusselt number based on channel hydraulic diameter Nu0 = baseline Nusselt number based on channel hydraulic diameter and measured with smooth top and bottom channel surfaces ReDh = Reynolds number based on bulk mean channel velocity and channel hydraulic diameter ReH = Reynolds number based on bulk mean channel velocity and channel height Toi = spatially averaged stagnation temperature at test section inlet Tw = surface temperature X = streamwise coordinate measured from upstream edge of test surface Z = spanwise coordinate measured from spanwise centerline of test surface

Wind identification along a flight trajectory, part 1: 3D-kinematic approach

This paper deals with the identification of the wind profile along a flight trajectory by means of a two-dimensional dynamic approach. In this approach, the wind velocity components are computed as the difference between the inertial velocity components and the airspeed components. The airspeed profile as well as the nominal thrust, drag, and lift profiles are obtained from the available DFDR measurements. The actual values of the thrust, drag, and lift are assumed to be proportional to the respective nominal values via multiplicative parameters, called the thrust, drag, and lift factors. The thrust, drag, and lift factors plus the inertial velocity components at impact are determined by matching the flight trajectory computed from DFDR data with the flight trajectory available from ATCR data. This leads to a least-square problem which is solved analytically under the additional requirement of closeness of the multiplicative factors to unity.

An investigation into the forces required to tow cables and sledges over Antarctic snow

The results of trials to investigate the forces required to tow cables and small sledges on Antarctic snow are discussed. Once moving, cables which were straight and towed at a constant speed showed drag factors of between 20 and 30%. For non-straight cables the drag factor could rise to 40% or more. A loaded sledge on a firm snow surface showed a drag factor of around 10%. The forces required to start the cables or sledges moving showed a much wider and less predictable range of drag factors.

The creeping motion of multiple spherical liquid drops

This paper deals with the drag factor of the multiple spherical liquid drops in the creeping motion by means of the Sampson singularities and collocation technique. The drag factors of the drops are calculated under distinct conditions: different number of liquid drops in the chain and different sphere spacing. From the results the influence of the viscosity ratio on the shielding effect and end effect are revealed. The convergence of the method is also studied in this paper.

Aerodynamic Characteristics of Thick Sharp Edged Cropped Delta and Gothic Wings giving Low Lift-Dependent Drag

For some years now an increasing amount of experimental and theoretical work has been done to obtain a deeper understanding of separated vortex flow associated with slender wings. Most of it has been concerned with flat plates or thin wings.Slender thin wings with leading-edge separation have high lift-dependent or vortex drags, and lift-dependent drag factors are usually well above unity. Thick symmetrical wings also have high values of lift-dependent drag factor. On a slender wing with leading edge separation, no leading edge thrust is obtained but by suitable! addition of thickness, the high suction peak underneath the main vortex can be made to act on a forward facing surface to give a reduction in drag.

Water performance of amphibious vehicles. Part 1—Drag and water speed: Part I—Drag and water speeds

This is the first of a two-part series which assembles the vehicle-environment relationships concerning the design of swimming vehicles. In this part drag and water speed factors influencing amphibious vehicles are analysed in some depth.

A method of determining diffusion coefficients and frictional drag factors in liquids

We propose a method of modeling the hydrodynamic friction of plates and the molecular diffusion of an impurity in a liquid medium by means of the phenomena of convection mass transport.

Propelling Nozzle Research

SummaryThe current interest in supersonic transport aircraft makes it appropriate to consider the problems of propulsion nozzle systems for high speed flight. The discussion will be confined mainly to this field of activity.In the absence of external drag and weight factors, the ideal configuration to maintain optimum thrust at all flight speeds would employ a mechanically variable area ratio nozzle. By such means the jet flow could be fully and properly expanded at all times.A practical design to accommodate such variations is inherently complex, and so an alternative solution using aerodynamic techniques has been sought. It is necessary to remember that the success of whatever method is eventually chosen must rest on its ability to combine a high performance at cruise with very small loss during other critical phases of the flight plan.This paper describes some of the results of a nozzle research programme aimed primarily at solving the above problem, with an attempt to explain the philosophy behind the aerodynamic techniques tried. Some discussion is given of the experimental difficulties in establishing a sufficiently accurate standard of measurement for design point performance. In a few chosen configurations experimental results have been extensively backed by theoretical studies.The need to demonstrate off-design behaviour in the presence of an external flow field is stressed, with special reference to the misleading results often obtained from static tests.Finally, some attention is given to the question of base bleed, with its repercussions on the installation of the propulsion nozzle in an aircraft.

Lift-Curve Slope and Induced Drag Factors of Large Aspect Ratio Straight-Tapered Wings

The difficulties of computing a solution to the Prandtl lifting line equation for large values of A/a0 are well-known, at least to any investigators who have tried. In attempting to deduce the loading over straight-tapered wings, like those used on sailplanes, the author has used an iterative method by which the nth. approximation to the downwash is obtained by a numerical integration based on the (n–l)th. approximation to the distribution of circulation. The main difficulty here is essentially one of making a good initial guess of circulation for the first approximation to the downwash.