Lift Angle Research Articles

The effect of dwell angle on vibration characteristics of camshaft bearing housings

Cam-follower mechanisms are affected by undesired dynamic forces which may disrupt the accuracy of the follower motion. These undesired dynamic forces create vibrations which cause noise, wear, and increasing operating costs for cam-follower mechanisms. Journal bearings are the most widely-used mechanical parts in internal combustion engines under high load and high operating speeds. In this study, the effect of the dwell angle on the vibration characteristics of camshaft bearing housings was investigated. Two camshafts having a 6 mm lift and different dwell angles were tested at operating speeds of 450, 900, 1350, 1920, and 2400 rpm. The collected data were analyzed in detail. It was observed that with the increasing of the camshaft rotational speed, vibration responses of greater magnitude were obtained. In general, the first and second peak values of the low dwell angle camshaft were higher than those of the high dwell angle camshaft.

Application of a Body-Weight-Supporting Kite for Sprint Running

Improvements in sprint performance at the top level require adaptations concerning force application because ground contact time diminishes with increasing velocity. Applied training methods and devices must provoke appropriate stimuli. A knowledge about positive and negative effects of these stimuli is vital for coaches. The purpose of this study was to determine the angle of attack and lifting and retarding forces of a novel sprint training device that supports the athlete's body weight (BW), thereby decreasing ground contact time during sprints. Three different kite sizes (1.10, 1.75, 2.25 m) were investigated. A bicycle was used to accelerate the National Aeronautics and Space Administration (NASA) parawings (NPW-120, NPW-150, and NPW-170) on an indoor track to acquire data at velocities between 6.5 and 10.5 m · s. During a 5-m interval of constant speed, the resultant force of the kite was recorded on a portable computer by a load cell. The angle of attack was determined by a high-speed camera, and the mean velocity in the 5-m sector was measured by a laser gauge. Lifting and retarding forces were derived from the resultant force and angle of attack. Quadratic regression equations for lifting and retarding forces, depending on the velocity, were calculated for all 3 NPWs. A clear difference (p < 0.001) depending on the kite size was revealed for lifting and retarding forces. These forces also indicated high correlation coefficients related to velocity (r > 0.98; p < 0.001), whereas the angle of attack remained almost constant across the entire velocity range in all NPWs, yielding a lift-to-drag ratio of 2.35. Because of the kite's small retarding forces, we recommend the application of the NPW during the high-speed phase of sprinting with lifting force probably counteracting adverse effects. By adding a towing system, the retarding force can be fine tuned, erased, or turned into overspeed assistance, thereby emphasizing BW support.

Application of Composite Core-Pulling Mechanism in Mobile Phone Cover Injection Mould

By process analyzing of the mobile phone cover, the overall mold structure and key design points for this product was introduced, the typical design methods for this kind of mold such as angle lift core-pulling mechanism and angle pin core-pulling mechanism were discussed. The part was ejected easily by adopting the angle lift mechanism and double ejection system. The working process of the injection mould was analyzed. Industrial practice proved that the action of the core-pulling mechanisms, ejector mechanisms and resetting mechanisms was stable and reliable.

Numerical Simulation of a Low Reynolds Number Airfoil

In this paper, a low Reynolds number airfoil (S1223) is the objective of the study. The Navier-Stokes equations were established to simulate the complex flow around a low Reynolds number airfoil, in which the turbulence model was used. The complex flow around the airfoil was simulated at 2x105 Reynolds number and its aerodynamic characteristics were analyzed. The relationship among lift coefficient, drag coefficient and angle of attack was studied.

Finite element simulation of moldboard–soil interaction

The efficiency of the tillage is measured by the power consumption or the tillage force or draught and the quality of the worked soil. The tillage forces are mainly a function of soil mechanical properties, working parameters of the tool (e.g. depth and speed) and tool geometry. In this paper we report on the numerical modeling of soil tillage. The finite element method (FEM) was used to model the cutting process of the soil using a moldboard. The surface geometry of the moldboard was measured with a 3D touch probe bench, also called coordinate measuring machine, and these data were used to construct the shape with SolidWorks design software. An elasto-plastic constitutive model was used for the soil. The generated surface of the plow was imported to Abaqus software as a discrete rigid body with a reference point at the tip of the moldboard. At this tip the reaction force with its three orthogonal components was calculated. The impact of the cutting angle (angle between the horizontal generatrix and the tillage direction) and the lift angle (angle between the moldboard surface and the horizontal line in an orthogonal section to the cutting edge) on draught force was investigated. The optimal values of these angles are in agreement with experimental data from the literature.

Piezo-stack vortex generators for boundary layer control of a delta wing micro-aerial vehicle

This paper presents an idea for the control of flow separation over solid surfaces by piezo-stack vortex generators. The vortex generators are small vibrating plates attached to the delta wing surface. A model of the micro-aerial vehicle (MAV) controlled by vortex piezo-generators is presented. The vortex generators are applied to produce the appropriate aerodynamical forces and moments controlling the flight of the aircraft. The efficiency of the vortex generators is proved by the wind tunnel test results. The oscillatory added lift and drag coefficients versus angle of attack are presented. The optimal vortex generator amplitude and frequency are investigated. Boundary layer control (BLC) for delta wing micro-aircraft increases the manoeuvrability and performance of the MAV.

Nonlinear Aeroelastic Behavior of Slender Wings Considering a Static Stall Model Based on Wagner Function

The aeroelastic behavior of high aspect ratio wings in an incompressible flow is investigated. The nonlinear nonplanar bending-bending-twisting motions of beam theory is used for the structural equations assuming large deformations with small strains, small Poisson effects, inextensional beam theory, and linear elastic material characteristics by neglecting warping and shear deformation. An Unsteady nonlinear aerodynamic static stall model based on the Wagner function is introduced and then is used for determination of aerodynamic loading of the wing. In this aerodynamic model, the static lift curve vs. angle of attack is approximated by a piece-wise curve and for each linear part of this curve a corrected Wagner theory is used. Combining these two types of formulation yields fully nonlinear integro-differentials aeroelastic equations of motion. The governing equations will be solved to predict the nonlinear aeroelastic response of a wing in the stall and post stall regions using Galerkin's method and a numerical method without the need of adding any aerodynamic state-space variables and their corresponding equations. The obtained equations are solved for some test cases and the obtained results are compared with the results given in the literature. Also a study is done to show effects of nonlinear aerodynamic static stall model on the limit cycle oscillations.

Testing Some Alpha-Models of Turbulence on Wing Profiles

In this paper some numerical simulations of the Navier-Stokes Equations (NSE) to test the novel NS-α and NS-ω turbulence models [1, , which conserve energy, enstrophy, and helicity, are presented. These algorithms verify more conservation properties than other implementations of the NSE, however their rotational form [ makes the scaling study of the coupling between the velocity and pressure errors with respect to the Reynolds number, a very interesting research line. Nowadays we are designing a wing profile in the context of Unmanned Aerial Vehicle (UAV) on incompressible flow conditions [. First a genetic algorithm (GA) is used to obtain the optimized design geometry and then the NS-α and NS-ω turbulence models are run to study its performance for different attack angles. The GA objective function evaluates the general potential theory of each wing section considered, because that requires less computational cost than the alternative of solving the NSE, and a wing design method proposed in [ is applied. Thus the optimized design geometry was found by evaluating the potential flow of all candidate solutions generated from the selection, crossover and mutation operators in each GA iteration. It takes the order of hundreds of simulations per iteration to evaluate all candidate solutions. Summarizing, two practical applications for a UAV are presented: the optimized design of an airfoil for environmental purposes, named CEANI airfoil, and the application of relevant turbulence models as NS-α and NS-ω in order to evaluate with accuracy the lift, drag and maximum angle of attack.

Optimized design for the plow of a submarine plowing trencher

The plow of the submarine plowing trencher is one of the main functional mechanisms, and its optimization is very important. The design parameters play a very significant role in determining the requirements of the towing force of a vessel. A multi-objective genetic algorithm based on analytical models of the plow surface has been examined and applied in efforts to obtain optimal design of the plow. For a specific soil condition, the draft force and moldboard surface area which are the key parameters in the working process of the plow are optimized by finding the corresponding optimal values of the plow blade penetration angle and two surface angles of the main cutting blade of the plow. Parameters such as the moldboard side angle of deviation, moldboard lift angle, angular variation of the tangent line, and the spanning length are also analyzed with respect to the force of the moldboard surface along soil flow direction. Results show that the optimized plow has an improved plow performance. The draft forces of the main cutting blade and the moldboard are 10.6% and 7%, respectively, less than the original design. The standard deviation of Gaussian curvature of moldboard is lowered by 64.5%, which implies that the smoothness of the optimized moldboard surface is much greater than the original.

Aerodynamic modelling of flapping flight using lifting line theory

PurposeThe purpose of the work is to design a flapping wing that generates net positive propulsive force and vertical force over a flapping cycle operating at a given freestream velocity. In addition, an optimal wing is designed based on the comparison of the force estimated from the quasi‐steady theory, with the wind‐tunnel experiments. Based on the designed wing configuration, a flapping wing ornithopter is fabricated.Design/methodology/approachThis paper presents a theoretical aerodynamic model of the design of an ornithopter with specific twist distribution that results generation of substantial net positive vertical force and thrust over a cycle at non‐zero advance ratio. The wing has a specific but different twist distribution during the downstroke and the upstroke that maintains the designed angle of attack during the strokes. The wing is divided into spanwise strips and Prandtl's lifting line theory is applied to estimate aerodynamic forces with the assumptions of quasi‐steady flow and the wings are without any dihedral or anhedral. Spanwise circulation distribution is obtained and hence lift is calculated. The lift is resolved along the freestream velocity and perpendicular to the freestream velocity to obtain vertical force and propulsive thrust force. Experiments are performed in a wind tunnel to find the forces generated in a flapping cycle which compares well with the theoretical estimation at low flying speeds.FindingsThe estimated aerodynamic force indicates whether the wing geometry and operating conditions are sufficient to carry the weight of the vehicle for a sustainable flight. The variation of the aerodynamic forces with varying flapping frequencies and freestream velocities has been illustrated and compared with experimental data that shows a reasonable match with the theoretical estimations. Based on the calculations a prototype has been fabricated and successfully flown.Research limitations/implicationsThe theory does not take into account the unsteady effects and estimates the aerodynamic forces at wing level condition. It doesn’t predict stall and ignores structural deformations due to aerodynamic loads. The airfoil section is only specified by the chord, zero lift angle of attack, lift slope, profile drag coefficient and angle of attack as given inputs. To fabricate a light weight wing that maintains a very accurate geometric twist and camber distribution as per the theoretical requirement is challenging.Practical implicationsUseful for designing ornithopter wing (preferably bigger) involving an unswept rigid spar with flapping and twisting.Originality/valueThe novelty of the present wing design is the appropriate spanwise geometric twisting about the leading edge spar.

A Simplified Palatal Lift Prosthesis for Neurogenic Velopharyngeal Incompetence

Velopharyngeal incompetence is a contributing factor to speech disorders and implies the presence of hypernasality, inappropriate nasal escape, and decreased air pressure during speech. One prosthetic treatment is a rehabilitative procedure employing a palatal lift prosthesis (PLP), which reduces hypernasality by approximating the incompetent soft palate to the posterior pharyngeal wall and consists of two parts, the anterior denture base and the palatal lifting plate, which are connected with steel wires; however, it seems difficult to reproduce the mobility of the soft palate in speaking, and it is therefore likely that the palatal lifting plate stimulates or oppresses the tissue of the soft palate and hinders rather than assists articulatory function. To avoid these disturbances we devised an adjustable PLP with a flexible conjunction between the denture base and the palatal lifting plate to obtain the optimal vertical lifting angle. The palatal plate was adapted to conform in a passive manner to the soft palate with light-cured resin. The designed PLP simplified the procedure and reduced the number of adjustments and visits.

Numerical Design of Leading Edge Flow Control over Swept High-Lift Airfoil

The present paper presents the numerical design of a leading edge flow control methodology over a swept two-element high-lift airfoil using steady state blowing through vortex generator jets. In baseline cases without flow control a turbulent leading-edge type of stall has been observed, therefore the vortex generator jets are applied at the leading edge of the airfoil to prevent separations and thus increase maximum lift and maximum angle of attack, respectively. The design of the flow control setup involves the variation of several geometrical and operational key parameters of the vortex generator jets, such as the pitch angle, skew angle, blowing ratio, sense of rotation and spanwise spacing of two adjacent jets. The results show that the numerical design of leading edge flow control is feasible for such wing arrangement. They show a significant degree of stall suppression over the swept high-lift airfoil.

Patient-Specific Rhytidectomy: Finding the Angle of Maximal Rejuvenation

Rhytidectomy is fundamentally an operation of tissue release and resuspension, although the manner and direction of suspension are subject to perpetual debate. The authors describe a method for identifying the angle of maximal rejuvenation during rhytidectomy and quantify the resulting angle and its relationship to patient age. Patients were prospectively enrolled; demographic data, history, and operative details were recorded. Rhytidectomies were performed by the senior author (AAJ). After complete elevation, the face-lift flap was rotated in a medially-based arc (0-90°) while attention was given to the submental area, jawline, and midface. The angle of maximal rejuvenation for each hemiface was identified as described, and the flap was resuspended. During redraping, measurements of vertical and horizontal skin excess were recorded in situ. The resulting angle of lift was then calculated for each hemiface using trigonometry. Symmetry between sides was determined, and the effect of patient age on this angle was assessed. Three hundred hemifaces were operated (147 women; 3 men). Mean age was 60 years (range, 37-80 years). Mean resulting angle for the cohort was 60° from horizontal (range, 46-77°). This was inversely correlated with patient age (r = -.3). Younger patients (<50 years, 64°) had a significantly more vertical angle than older patients (≥70 years, 56°; P < .0002). No significant intersubject difference was found between hemifaces (P = .53). The authors present a method for identifying the angle of maximal rejuvenation during rhytidectomy. This angle was more superior than posterior in all cases and is intimately related to patient age. Lasting results demand a detailed anatomical understanding and strict attention to the direction and degree of laxity.

Influence of Rounded Corners on Flow Interference Due to Square Cylinders Using Immersed Boundary Method

Abstract The influence of rounded corners on the aerodynamic forces and flow interference has been studied in detail for a uniform flow past two side-by-side arranged square cylinders. The Reynolds number (Re) based on the cylinder diameter (D) and free stream velocity (U∞) is 100. Numerical simulations are carried out for seven different transverse gap ratios (T/D), each with a minimum and maximum corner radius. An inbuilt finite difference code with staggered arrangement of flow variables is used to discretize the governing equations. The concept of immersed boundary method (IBM) is employed to simulate flow around rounded corners using the regular Cartesian grids. The computational code was validated for flow past an isolated circular cylinder, square cylinder, and two equal sized circular cylinders and the results were found to be in very good agreement with available literatures. In the present study, results in terms of the mean and rms values of lift and drag coefficients, Strouhal number, phase diagrams, and contours of streamlines and vorticity are presented. As the corner radius is increased, a reduction in the drag force is observed. There exists a significant effect of gap ratio and corner radius on the phase angle of lift and drag coefficients. Three different flow patterns, namely the single bluff body flow, biased gapside flow, and two independent bluff body flows, were observed from this study.

Nonlinear Aeroelastic Behavior of Slender Wings Considering a Static Stall Model Based on Wagner Function

The aeroelastic behavior of high aspect ratio wings in an incompressible flow is investigated. The nonlinear nonplanar bending-bending-twisting motions of beam theory is used for the structural equations assuming large deformations with small strains, small Poisson effects, inextensional beam theory, and linear elastic material characteristics by neglecting warping and shear deformation. An Unsteady nonlinear aerodynamic static stall model based on the Wagner function is introduced and then is used for determination of aerodynamic loading of the wing. In this aerodynamic model, the static lift curve vs. angle of attack is approximated by a piece-wise curve and for each linear part of this curve a corrected Wagner theory is used. Combining these two types of formulation yields fully nonlinear integro-differentials aeroelastic equations of motion. The governing equations will be solved to predict the nonlinear aeroelastic response of a wing in the stall and post stall regions using Galerkin's method and a numerical method without the need of adding any aerodynamic state-space variables and their corresponding equations. The obtained equations are solved for some test cases and the obtained results are compared with the results given in the literature. Also a study is done to show effects of nonlinear aerodynamic static stall model on the limit cycle oscillations.

Aerodynamic Investigations of Low-Aspect-Ratio Thin Plate Wings at Low Reynolds Numbers

ABSTRACTTo realize the relationship between flow structures of wingtip vortices and post stall characteristics of low aspect-ratio wings, this paper experimentally studies the aerodynamic characteristics and the corresponding flow structures of the rectangular thin-plate wings at Reynolds numbers between 104 and 105. The aerodynamic properties to be studied include lift, drag, slopes at linear and nonlinear range of the lift curves and lift-to-drag ratios of the tested wings with the aspect ratio varying from 1.0 to 3.0. The flow structures regarding the leading-edge separation vortices and wingtip vortices at upper surface and near-wake regions of the wings are also investigated by smoke-wire visualization. Results indicate that the high stall angle of attack and vortex lift are clearly manifested to induce the nonlinear increase in the lift curves as the aspect ratio reaches less than 1.6. This phenomenon is specifically observed to augment the aerodynamic properties with the decrease of the aspect ratio. Additionally, the corresponding flow visualization also indicates that the wingtip vortices and the areas of highly affected regions are duly increased with the increase of the angle of attack up to 40°, which makes certain that the extra increase of the nonlinear lift results from these vortices. This result can be practically applied to the planform design for unmanned aerial vehicles.

An Alternate Approach For Geometrical Construction Of Subsonic Airfoil With Numerical Investigation

Although the equations for the flat plate, circular arc and symmetrical Joukowski airfoils are simple and direct those of the cambered airfoil are complicated and may be by-passed only because an ingenious geometrical method exist which may be used to find both the profile of the airfoil and its pressure distribution namely Karmann-Treffz geometrical construction. An Alternate geometrical method has been proposed in this paper and using fitting line theory, the equation has been arrived and performances of airfoils are studied. Few interesting results regarding co-efficient of lift, co-efficient of moment at leading edge and quarter chord, zero lift angle, lift co-efficient at zero lift angle has been discussed and compared by using design foil and XFLR.

Design and Research on Micro Pure Electric Garbage Transfer Vehicle

Based on the analysis of characteristics and Application requirements, one type of micro pure electric garbage transfer vehicle was designed. The power layout program, chassis layout and hydraulic lifting mechanism were researched to meet the driving safety need and automobile ride. The McPherson independent front suspension and the coil spring integral rear suspension were selected as the suspension program. The type of motor front and front drive was the arrangement of power system. The ladder frame chassis was selected for its high strength and low cost and the finite element analysis of frame was executed to verify the strength. The lifting mechanism was the key of the vehicle, one integrated hydraulic lifting mechanism was selected and the lifting time and angle and cylinder diameter were calculated. The tests confirm the sample vehicle being of reliable design and good performance.

EFFECT OF SOME MECHANICAL LIFTING TYPES ON THE QUALITATIVE &amp; QUANTITATIVE LOSS OF POTATO CROP IN NINEVAH GOVERNORATE

This research aimed to study some of the technical and economical effects including the use of two kinds of potato lifters with one stage of suspended type, the first foreigner made (Finnish) type Tume and the second local designed by the researcher. The research was carried out in mixed soils for both equipments. The angle of lifting was (25) for both equipments and seasons. The results were analyzed statistically by using the factorial experiment with in split plot design with three replications. The following conclusions were depicted. In the first season the results showed that there are no significant differences concerning the effect of lifting equipments on the studied properties In the second season the results showed that there are significant differences concerning the effect of lifting equipments on some of the studied properties, where the local equipment showed slightly higher significance than the foreigner one in the damaged tubers and lifter potatoes properties, but the foreigner equipment showed higher significance concerning the quantitative loss and there were no significant differences in other studied properties. In the mean of the two seasons the results showed that the effect of seasons was higher significantly than most of the studied properties. The first season showed higher significance regarding the undamaged and lifted potatoes than the 2nd season, while the one later showed slight difference concerning the damaged tubers and the qualitative and quantitative losses and no great significant difference in the damaged tubers.

Small-incision orbicularis–levator fixation technique: A modified double-eyelid blepharoplasty for treating trichiasis in young Asian patients

Upper-eyelid trichiasis often occurs with a single puffy eyelid or shallow eyelid crease in young Asian patients. This study presents a novel modified trichiasis correction method to simultaneously treat trichiasis and create a natural eyelid crease. It combines the modified small-incision debulking procedure and the orbicularis-levator fixation technique. The eyelash lift angle (LA), body curl angle (BCA) and end curl angle (ECA) were quantitatively analysed. A total of 90 patients (152 trichiasis eyelids) were followed up for approximately 22 months. The LA changed from 24.32°±9.21°-54.12°±10.32° in the nasal section of the eyelid (section 1), from 21.03°±11.34°-52.03°±10.56° in the middle section of the eyelid (section 2) and from 23.31°±8.12°-63.15°±8.43° in the temporal section of the eyelid (section 3). All patients were satisfied with the eyelid-fold appearance. In conclusion, for young Asian patients with upper-eyelid trichiasis, the small-incision orbicularis-levator fixation technique is able to acquire a stable up-curved position of the eyelashes and satisfactory aesthetic results.