Longitudinal Angle Research Articles

Empirical correlations for mixed convection heat transfer through a fin array based on various orientations

The transfer of heat by the fins is influenced by the change of the direction of the fins. This paper investigates study the effect of the direction of longitudinal fins on a three-dimensional convection heat transfer in a rectangular channel and also study the effect of the lateral and longitudinal inclination of the rectangular channel. The Grashof range from 5 × 108 to 109, Reynolds from 1000 to 2300 and Prandtl 0.71. The bottom surface of the channel is exposed to constant heat flux, while other walls are isolated. Two cases are investigated. In case one, measurements were conducted for a lateral inclination of the channel, with a range of α = 0°,30°,60°, and 90°. Case two studied the longitudinal inclination of the channel, with the lateral inclination angle fixed at α = 90° and the longitudinal inclination angle Ө = 0°, 30°, 60°, and 70°. The dimensionless of fin height was Hf/H = 0.6, and the fin spacing was S/H = 0.17. The experimental results show that the coefficient of the heat transfer for lateral inclination (α = 0°) was greater than that for a sideways orientation (α = 90°). Additionally, the average coefficient of heat transfer for both the lateral and longitudinal inclination case is increased with the longitudinal inclination angle. The empirical equations are obtained based on the experimental results. These equations correlated the Nusselt number as a dependent variable of the orientations angles, Reynolds number, and the Grashof number, these equations are consistent with experimental results.

Analysis of the position of EndoAnchor implants in therapeutic use during endovascular aneurysm repair

ObjectiveThe aim of this study was to analyze the penetration depth, angles, distribution, and location of deployment of individual EndoAnchor (Medtronic Vascular, Santa Rosa, Calif) implants. MethodsEighty-six primary and revision arm patients (procedural success, 53; persistent type IA endoleak, 33) treated for type IA endoleaks with a total of 580 EndoAnchor implants from a subset of the Aneurysm Treatment Using the Heli-FX Aortic Securement System Global Registry (ANCHOR) were included in this study. Procedural success was defined as the absence of a type IA endoleak on the first postprocedural computed tomography scan after the EndoAnchor implantation procedure. Endograft malapposition along the circumference was assessed at the first postoperative computed tomography scans and expressed as clock-face range and width in degrees and normalized such that the center was translated to 0 degrees. The position and penetration of each EndoAnchor implant were measured as the clock-face orientation. EndoAnchor implant penetration into the aortic wall was categorized as follows: good penetration, ≥2 mm; borderline penetration, <2 mm or ≥2-mm gap between the endograft and aortic wall; or no penetration. The orthogonal and longitudinal angles between the EndoAnchor implant and the interface plane of the aortic wall were determined. Location of deployment was investigated for each EndoAnchor implant and classified as maldeployed when it was above the fabric or in a gap >2 mm between the endograft and aortic wall due to >2-mm thrombus or positioning of the EndoAnchor implant below the aortic neck. ResultsA total of 170 (29%) EndoAnchor implants had maldeployment and were therefore beyond recommended use and not useful. After EndoAnchor implantation, the procedural success and persistent type IA endoleak groups had 3 (1%) and 4 (2%) EndoAnchor implants positioned above the fabric as well as 60 (18%) and 103 (42%) placed in a gap >2 mm, respectively. The amount of EndoAnchor implants with good, borderline, and no penetration was significantly different between both groups (success vs type IA endoleak) after exclusion of maldeployed EndoAnchor implants (235 [87.4%], 14 [5.2%], and 20 [7.4%] vs 97 [68.8%], 18 [12.8%], and 26 [18.4%], respectively; P < .001). Good penetration EndoAnchor implants were more closely aligned with a 90-degree orthogonal angle than the borderline penetration and nonpenetrating EndoAnchor implants. The longitudinal angle was more distributed, which was observed through all three penetration groups. ConclusionsIn this subcohort of ANCHOR patients, almost 30% of the EndoAnchor implants had maldeployment, which may be prevented by careful preoperative planning and measured intraoperative deployment. If endoleaks are due to >2-mm gaps, EndoAnchor implants alone may not provide the intended sealing, and additional devices should be considered.

Estimation of Longitudinal Force and Sideslip Angle for Intelligent Four-Wheel Independent Drive Electric Vehicles by Observer Iteration and Information Fusion.

Exact estimation of longitudinal force and sideslip angle is important for lateral stability and path-following control of four-wheel independent driven electric vehicle. This paper presents an effective method for longitudinal force and sideslip angle estimation by observer iteration and information fusion for four-wheel independent drive electric vehicles. The electric driving wheel model is introduced into the vehicle modeling process and used for longitudinal force estimation, the longitudinal force reconstruction equation is obtained via model decoupling, the a Luenberger observer and high-order sliding mode observer are united for longitudinal force observer design, and the Kalman filter is applied to restrain the influence of noise. Via the estimated longitudinal force, an estimation strategy is then proposed based on observer iteration and information fusion, in which the Luenberger observer is applied to achieve the transcendental estimation utilizing less sensor measurements, the extended Kalman filter is used for a posteriori estimation with higher accuracy, and a fuzzy weight controller is used to enhance the adaptive ability of observer system. Simulations and experiments are carried out, and the effectiveness of proposed estimation method is verified.

Foot structure and knee joint kinetics during walking with and without wedged footwear insoles

The relationship between static foot structure characteristics and knee joint biomechanics during walking, or the biomechanical response to wedged insoles are currently unknown. In this study, 3D foot scanning, dual X-ray absorptiometry and gait analysis methods were used to determine structural parameters of the foot and assess their relation to knee joint loading and biomechanical response to wedged insoles in 30 patients with knee osteoarthritis. In multiple linear regression models, foot fat content, height of the medial longitudinal arch and static hind foot angle were not associated with the magnitude of the knee adduction moment (R2 = 0.24, p = 0.060), knee adduction angular impulse (R2 = 0.21, p = 0.099) or 3D resultant knee moment (R2 = 0.23, p = 0.073) during gait. Furthermore, these foot structure parameters were not associated with the patients’ biomechanical response to medial or lateral wedge footwear insoles (all p < 0.01). These findings suggest that static foot structure is not associated with gait mechanics at the knee, and that static foot structure alone cannot be utilized to predict an individual’s biomechanical response to wedged footwear insoles in patients with knee osteoarthritis.

Papillary muscles contribute significantly more to left ventricular work in dilated hearts.

Left ventricular (LV) dilatation results in increased sphericity and affects position and orientation of papillary muscles (PMs), which may influence their performed work. The aim of this study was to assess the contribution of PM to LV function and its changes with dilatation. Fifteen sheep were investigated. Ten animals were subjected to 8 weeks of rapid (180 bpm) pacing, inducing LV dilatation. Five animals served as controls. High-resolution gated computed tomography was performed to assess LV volumes, left ventricular ejection fraction (LVEF), global longitudinal strain (GLS), sphericity index, and PM angle, width and fractional shortening. 18F-fluorodeoxyglucose positron emission tomography (PET) was used to measure glucose metabolism as surrogate of regional myocardial work. Spatial resolution of PET images was maximized by electrocardiogram- and respiratory-gating. 18F-fluorodeoxyglucose uptake was measured in PM and compared with remaining left ventricular myocardium (MYO) to obtain a PM/MYO ratio. Animals with dilated heart had a more spherical left ventricle, with reduced LVEF (P < 0.0001) and GLS (P < 0.0001). In dilated hearts, PET analysis revealed a higher contribution of both PM to LV myocardial work (P < 0.0001); and PM angle towards LV wall correlated with PM work, together with PM width and the LV sphericity index. Sphericity index and posterior PM angle were strongest determinants of posterior PM/MYO ratio (R2 = 0.754; P < 0.0001), while anterior PM/MYO was mostly determined by sphericity index and the PM width (R2 = 0.805; P < 0.0001). In dilated hearts, PM contribute relatively more to LV myocardial work. We hypothesize that this is caused by the more cross-sectional orientation of the subvalvular apparatus, which leads to a higher stress on the PM compared with the spherical LV walls. The reduced cross-sectional area of the PM may further explain their increased stress.

Revisiting slope influence in turbulent bedload transport: consequences for vertical flow structure and transport rate scaling

Gravity-driven turbulent bedload transport has been extensively studied over the past century in regard to its importance for Earth surface processes such as natural riverbed morphological evolution. In the present contribution, the influence of the longitudinal channel inclination angle on gravity-driven turbulent bedload transport is studied in an idealised framework considering steady and uniform flow conditions. From an analytical analysis based on the two-phase continuous equations, it is shown that: (i) the classical slope correction of the critical Shields number is based on an erroneous formulation of the buoyancy force, (ii) the influence of the slope is not restricted to the critical Shields number but affects the whole transport formula and (iii) pressure-driven and gravity-driven turbulent bedload transport are not equivalent from the slope influence standpoint. Analysing further the granular flow driving mechanisms, the longitudinal slope is shown to not only influence the fluid bed shear stress and the resistance of the granular bed, but also to affect the fluid flow inside the granular bed – responsible for the transition from bedload transport to debris flow. The relative influence of these coupled mechanisms allows us to understand the evolution of the vertical structure of the granular flow and to predict the transport rate scaling law as a function of a rescaled Shields number. The theoretical analysis is validated with coupled fluid–discrete element simulations of idealised gravity-driven turbulent bedload transport, performed over a wide range of Shields number values, density ratios and channel inclination angles. In particular, all the data are shown to collapse onto a master curve when considering the sediment transport rate as a function of the proposed rescaled Shields number.

Stability Analysis of Agricultural Off-Road Vehicles.

Vehicle rollovers cause many agricultural work-related fatalities each year. Tractors, off-road utility vehicles (ORUVs), zero turn radius (ZTR) mowers, and all-terrain vehicles (ATVs) can all become involved in fatal rollovers. The rollover tendency of these vehicles was evaluated using static lateral and longitudinal stability angles. Center of gravity locations were measured with the lift axle method, and lateral and longitudinal stability angles were calculated for four ATVs, five ORUVs, four ZTR mowers, and four lawn tractors. Stability angles were calculated for loaded and unloaded vehicle conditions. Loading vehicles with ballast and operators can substantially decrease lateral and longitudinal stability angles. Stability angles for these vehicles and for five full-size agricultural tractors were compared. All loaded and unloaded, lateral and longitudinal stability angles determined met the appropriate ANSI requirements.

Reliable Sideslip Angle Estimation of Four-Wheel Independent Drive Electric Vehicle by Information Iteration and Fusion

Accurate estimation of longitudinal force and sideslip angle is significant to stability control of four-wheel independent driven electric vehicle. The observer design problem for the longitudinal force and sideslip angle estimation is investigated in this work. The electric driving wheel model is introduced into the longitudinal force estimation, considering the longitudinal force is the unknown input of the system, the proportional integral observer is applied to restructure the differential equation of longitudinal force, and the extended Kalman filter is utilized to estimate the unbiased longitudinal force. Using the estimated longitudinal force, considering the unknown disturbances and uncertainties of vehicle model, the robust sideslip angle estimator is proposed based on vehicle dynamics model. Moreover, the recursive least squares algorithm with forgetting factor is applied to vehicle state estimation based on the vehicle kinematics model. In order to integrate the advantages of the dynamics-model-based observer and kinematics-model-based observer and improve adaptability of observer system in complex working conditions, a vehicle sideslip angle fusion estimation strategy is proposed. The simulations and experiments are implemented and the performance of proposed estimation method is validated.

Stability of long combination vehicles

In general, long combination vehicles (LCVs) show poor performance with regard to stability, and this has been the focus of many studies around the world. Some characteristics such as the suspension topology, tyres, chassis and fifth wheel have been analysed, separately, to determine their influence on the vehicle stability calculation. Most vehicle stability models are developed in two dimensions, and they do not consider the longitudinal aspects of the vehicle and the road such as the stiffness of the chassis, the gravity centre location and the longitudinal slope angle of the road. In this context, the aim of this study was to develop a three-dimensional mechanism model of the trailer to represent all of these characteristics and their influence on the lateral stability.

UAV Flight Stability Control Method Based on Steady - state Error Correction0

UAV flight stability control system is a multivariable, non - linear, strongly coupled system, the steady-state error is easy to occur with the traditional fuzzy control method. An UAV flight stability control method is proposed based on steady - state error correction, the steady state dynamic model of UAV flight is constructed, and the control constraint model is constructed with the roll angle, the pitch angle, the longitudinal inclination angle and the acceleration as the constraint parameters. The construction of UAV flight stability control objective function is obtained, and the linearization treatment is carried out near the equilibrium point of the flight of the unmanned aerial vehicle, and the equivalent control law of the sliding mode surface is constructed. Based on the conventional synovial surface, an integral term of tracking error is added to reduce the steady-state error and realize adaptive correction of flight parameters. The simulation results show that the stability of the flight control of the UAV is better by the method, and the self - adaptive correction capability of the flight state parameters is strong.

Improvement of longitudinal fins configuration in latent heat storage systems

Abstract In this study, the consequences of variation of the longitudinal fins angle on the heat transfer improvement during phase change are investigated. Therefore, the melting process of RT 35 as a phase change material is studied for triple-fin and double-fin cases for different angles and the results are compared with of bare tube case. Results indicated that due to the natural convection domination, the upper fin does not leave a great effect on the total melting time. Considering the triple-fin heat exchangers, as the fins angle increases from 60° to 120°, the total melting time reduces. However, when double-fin cases are under consideration, reducing the angle from 150° to 45° results in melting time reduction. More reduction in the angle increases the total melting time. Results also showed that the best cases among triple-fin cases and among the double-fin cases result in 22.5 and 62% reduction in melting time with respect to the simple heat exchanger.

Constitutive modeling of human femoropopliteal artery biaxial stiffening due to aging and diabetes.

We have analyzed n=744 human femoropopliteal artery (FPA) specimens using biaxial tensile testing to derive constitutive description of FPA aging in diabetic and non-diabetic subjects. The proposed model allows determination of FPA mechanical properties for subjects of any given age in the range of 13-82years. These results contribute to understanding of FPA pathophysiology and can help improve fidelity of computational models investigating device-artery interaction in peripheral arterial disease repair by providing more personalized arterial properties. In addition, they can guide the development of new materials tunable to diabetic and non-diabetic arteries.

Parametric study of the small scale linear Fresnel reflector

Abstract This paper addresses the influence of the transversal and longitudinal parameters in the performance of a small scale linear Fresnel reflector (SSLFR) without longitudinal movement. The main purpose of this study is to show the influence of the design parameters (receiver height, mirror length, and mirror width) on the energy absorbed by the absorber tube. In addition, the influence of these parameters on the shading of the absorber tube is also analysed. Different configurations are analysed regarding the longitudinal angle that the mirrors and the absorber tube form with the horizontal plane. Each of these configurations is analysed considering the optimal length and longitudinal position of the absorber tube. Numerical simulations show the influence of mirror width, mirror length, and receiver height on the energy absorbed. The simulations allow us to analyze the monthly variation of this influence throughout the year, considering also the effect of the latitude. A sensitivity analysis is also carried out in order to evaluate the importance of the parameters.

Dependence of the Peak Fluxes of Solar Energetic Particles on CME 3D Parameters from STEREO and SOHO

Abstract We investigate the relationships between the peak fluxes of 18 solar energetic particle (SEP) events and associated coronal mass ejection (CME) 3D parameters (speed, angular width, and separation angle) obtained from SOHO, and STEREO-A/B for the period from 2010 August to 2013 June. We apply the STEREO CME Analysis Tool (StereoCAT) to the SEP-associated CMEs to obtain 3D speeds and 3D angular widths. The separation angles are determined as the longitudinal angles between flaring regions and magnetic footpoints of the spacecraft, which are calculated by the assumption of a Parker spiral field. The main results are as follows. (1) We find that the dependence of the SEP peak fluxes on CME 3D speed from multiple spacecraft is similar to that on CME 2D speed. (2) There is a positive correlation between SEP peak flux and 3D angular width from multiple spacecraft, which is much more evident than the relationship between SEP peak flux and 2D angular width. (3) There is a noticeable anti-correlation (r = −0.62) between SEP peak flux and separation angle. (4) The multiple-regression method between SEP peak fluxes and CME 3D parameters shows that the longitudinal separation angle is the most important parameter, and the CME 3D speed is secondary on SEP peak flux.

A new mini-CPC with a U-type evacuated tube under thermal and optical investigation

Abstract In this study a mini-CPC with a U-type evacuated tube and a cylindrical absorber is analyzed optically and thermally. The operation of the collector was simulated in horizontal position for ten different inlet water temperatures (10–100 °C per 10 °C) while the heat from the sun was considered to be perpendicular to the aperture plane of the reflector for the thermal analysis part. The thermal efficiency and the overall heat loss coefficient of the collector were calculated and the temperature fields of the absorber, the cover and the water were determined. Moreover, the convection between the water and the tube was examined and compared to a specific model of heat transfer theory. Particularly, the heat transfer coefficient values resulted from the simulation were found to diverge about 6% from the theoretical solution. In addition, the optical efficiency was investigated for several transversal and longitudinal incident angles of the sun rays while a similar collector with a flat absorber was used in order to compare its optical performance to the examined collector. It was found that the longitudinal incident angle modification did not diversify the collectors' performances significantly while the transversal one revealed that the circular absorber configuration appears greater optical performance compared to the flat one. Moreover, the optical performance of the specific collector was compared with the respective of two other CPCs from literature studies and found to exceed them. Also, the secondary flows inside the bend of the U-pipe were determined and explained. The design and the simulation of the collector have been done with Solidworks.

Main Rotor Trimming Using CFD Method in Forward Flight

In this paper a CFD trimming method was proposed and compared with wind tunnel experiment and blade element method. NASA’s generic ROBIN helicopter model was adopted for transient simulations to get the final main rotor trimming condition. Totally three steps were applied to CFD method, one being no cyclic pitch motion, one being pure longitudinal cyclic pitch motion and the other one being pure lateral cyclic pitch motion. At the same time, a simple linear equation system between the roll and pitching moment was adopted to get the final longitudinal and lateral cyclic pitch angles for the main rotor through these three steps. An overset grid approach was used where the volume around each blade was modeled in an individual overset grid region. The rotor rotation was resolved with 3 degree per time-step. Turbulence was modeled with the well known SST K-omega model with 2nd order convection. The helicopter was in straight forward flight with an advance ratio of μ=0.151. Three sources of stick angles, which are also calling rotor trimming angles, were shown and compared with each other. And the corresponding results were also plotted with type of history plot in CFD condition. In the simulations the results became quasi periodic after about 1.5 rotations and 4 rotor rotations were simulated for each case. The pitch moment coefficient and roll moment coefficient were all trimmed to zero by CFD trimming method while moments were not be removed thoroughly in other two sources condition. So, it is concluded that CFD trimming method has an ability to trim helicopter main rotor in forward flight.

국내 연안 카페리 차량 고박 장치 안전성에 관한 연구: 제2부 가속도 예측 방법에 따른 고박 안전도 비교 연구

For a carferry with a displacement of 1,633 tonf, a seakeeping analysis-based direct load approach (DLA) was used in Part I of these series, where the final deliverable was the long-term probabilistic acceleration components. In Part II of these series, the tangential acceleration components are explained based on two approaches: a standard called the IMO CSS code and simple formulas with the probable maximum roll and pitch rotations. The subsequent tangential acceleration-induced external force components are also introduced for these two approaches. The lashing strength components were selected from the IMO CSS code. It was assumed that two different vehicles (a car and a truck) were stowed at the most distant locations on the main deck to assume the largest tangential acceleration components and were secured with four steel wires with longitudinal and transverse lashing angles of <TEX>$45^{\circ}$</TEX>. Four cases were considered, with different methods for predicting the acceleration components and different tools for the external loads and lashing strengths involved: cases Rule-LS (rule-based maximum probable roll and pitch angles for predicting the acceleration components in conjunction with LashingSafety), DLA-LS (seakeeping-based long-term acceleration components with LashingSafety), CSS-LC (IMO CSS code-based acceleration components using LashCon), and CSS-LS (IMO CSS code-based acceleration components using LashingSafety). In terms of the acceleration and external force components, the CSS-LC and CSS-LS results are more than two times the results of Rule-LS. Thus, when the external forces and lashing strengths are evaluated using CSS-LC and CSS-LS, the truck needs more lashing wires, while Rule-LS and DLA-LS predict that the present lashing configuration is on the safe side.

Increasing the flexural capacity of RC beams using steel angles and pre‐tensioned stainless steel ribbons

AbstractThis article presents an experimental programme on reinforced concrete beams retrofitted with steel angles and pre‐stressed stainless steel ribbons to increase their flexural strength and ductility. Two different configurations of the steel ribbon were designed, and two companion specimens for each type considered were subjected to a four‐point bending test to facilitate a direct comparison in the analysis of the effectiveness of the retrofitting technique. The influence of longitudinal steel angles and transverse stainless steel ribbons is analysed, and the concrete confinement due to stainless steel ribbons examined. The strengthened beams show remarkable increments in flexural strength and ductility with respect to the as‐built beam. Moreover, a simple cross‐sectional model was adopted to calculate the flexural strength; then sophisticated numerical tools were used to reproduce both the experimental load‐displacement curve and crack pattern for each specimen.

Main helicopter rotor trimming using computational fluid dynamics method in forward flight

In this paper, a computational fluid dynamics trimming method is proposed and compared with wind tunnel experiment and the blade element method. The NASA’s generic ROBIN helicopter model is adopted for transient simulations to obtain the final main rotor trimming conditions. Totally three steps were applied to the computational fluid dynamics method. The first step is associated with no cyclic pitch motion, the second is regarding pure longitudinal cyclic pitch motion and the last is concerning with pure lateral cyclic pitch motion. At the same time, a simple linear equation system between the roll and pitching moment was established to get the final longitudinal and lateral cyclic pitch angles for the main rotor through the above three steps. An overset grid approach was used where the volume around each blade was modeled in an individual overset grid region. The rotor rotation was resolved with three degrees per time-step. Turbulence was modeled with the well-known SST K-omega model with second-order convection. The helicopter was in straight forward flight with an advance ratio of [Formula: see text]. Three sources of stick angles, which are also called rotor trimming angles, were shown and compared with each other. And the corresponding results were also plotted with a type of history plot in the computational fluid dynamics condition. In the simulations, the results became quasi periodic after about 1.5 rotations and four rotor rotations were simulated for each case. The pitch moment coefficient and roll moment coefficient were all trimmed to about zero by the computational fluid dynamics trimming method while moments were not removed thoroughly in the other two source conditions.

Unexpected spatial intensity distributions and onset timing of solar electron events observed by closely spaced STEREO spacecraft

We present multi-spacecraft observations of four solar electron events using measurements from the Solar Electron Proton Telescope (SEPT) and the Electron Proton Helium INstrument (EPHIN) on board the STEREO and SOHO spacecraft, respectively, occurring between 11 October 2013 and 1 August 2014, during the approaching superior conjunction period of the two STEREO spacecraft. At this time the longitudinal separation angle between STEREO-A (STA) and STEREO-B (STB) was less than 72°. The parent particle sources (flares) of the four investigated events were situated close to, in between, or to the west of the STEREO’s magnetic footpoints. The STEREO measurements revealed a strong difference in electron peak intensities (factor ≤12) showing unexpected intensity distributions at 1 AU, although the two spacecraft had nominally nearly the same angular magnetic footpoint separation from the flaring active region (AR) or their magnetic footpoints were both situated eastwards from the parent particle source. Furthermore, the events detected by the two STEREO imply a strongly unexpected onset timing with respect to each other: the spacecraft magnetically best connected to the flare detected a later arrival of electrons than the other one. This leads us to suggest the concept of a rippled peak intensity distribution at 1 AU formed by narrow peaks (fingers) superposed on a quasi-uniform Gaussian distribution. Additionally, two of the four investigated solar energetic particle (SEP) events show a so-called circumsolar distribution and their characteristics make it plausible to suggest a two-component particle injection scenario forming an unusual, non-uniform intensity distribution at 1 AU.