Tip Loss Research Articles

Male Revision Rhinoplasty: Pearls and Surgical Techniques

Male revision rhinoplasty surgery is the most difficult and challenging procedure that facial plastic surgeons perform because males usually have thick nasal skin, which is more difficult to re-support and project the nasal tip, and often have high or unrealistic expectations. The primary etiology for the need for male revision rhinoplasty is a primary rhinoplasty with aggressive lower lateral cartilage reduction that causes tip ptosis and loss of projection. The goal to an aesthetically pleasing revision rhinoplasty is to re-create adequate tip projection and an intact strong tripod complex. Following tip reconstruction, the height and width of the dorsum should be set. For male revision nasal surgery, a clear and thorough knowledge of nasal anatomy, function, and surgical techniques is paramount. Having an extensive preoperative discussion including expectations, outcomes, and a detailed list of potential complications with the patient can prevent physician-patient mis-communication. Prior to surgery, review the examination, previous operative summary, photographs, nasal analysis sheet, problem list, and plan and then proceed with the surgical treatment.

A theoretical investigation on the vibrational characteristics and torsional dynamic response of circumferentially cracked turbo-generator shafts

Turbo-generator shafts are often subjected to complex dynamic torsional loadings, resulting in generation and propagation of circumferential cracks. Mode III fatigue crack growth generally results in a fracture surface consisting of peaks and valleys, resembling a factory roof. The fracture surface roughness depends on the material microstructure, the material yield strength, and the applied cyclic torque amplitude. This crack pattern can severely affect the vibration characteristics of the shafts. The accurate evaluation of the torsional dynamic response of the turbo-generator shafts entails considering the local sources of energy loss in the crack vicinity. The two most common sources of the energy loss are the local energy loss due to the plasticity at the crack tip and frictional energy loss due to interaction of mutual crack surfaces. A theoretical procedure for evaluating the values of the system loss factors corresponding to these sources of energy loss is presented. Furthermore, the local flexibility is obtained by evaluating the resistance of the cracked section of the shaft to the rotational displacement. The shaft material is assumed to be elastic perfectly plastic. The effects of the applied Mode III stress intensity factor and the crack surface pattern parameters on the energy loss due to the friction and the energy loss due to the plasticity at the crack tip are investigated. The results show that depending on the amplitude of the applied Mode III stress intensity factor, one of these energy losses may dominate the total energy loss in the circumferentially cracked shaft. The results further indicate that the torsional dynamic response of the turbo-generator shaft is significantly affected by considering these two sources of the local energy loss.

Tip Loss Correction for Actuator/Navier–Stokes Computations

A new tip loss correction, initially developed for 1D Blade Element/Momentum (BEM) computations (submitted to Wind Energy), is now extended to 2D Actuator Disc/Navier–Stokes (AD/NS) computations and 3D Actuator Line/Navier–Stokes (AL/NS) computations. In the paper, it is shown that the tip loss correction is an important and necessary step for actuator/Navier–Stokes models. Computed results are compared to experimental data and to results from BEM computations using the new tip correction as well as the original one of Glauert (Aerodynamic Theory, Dover, New York, Chap. VII, Div. L, pp. 251–268). From the results it is concluded that the tip loss correction has been correctly employed in the Navier–Stokes based actuator models. The results also demonstrate that the difference between actuator line and actuator disk-based models may increase, especially for flows at a low tip speed ratio. Since the flows at a low tip speed ratio are too far to be considered as axisymmetrical flows, the actuator disk models that are based on axisymmetrical flow behaviors may not be valid.

Tip loss corrections for wind turbine computations

As an essential ingredient in the blade element momentum theory, the tip loss effect of rotors plays an important role in the prediction of wind turbine performance. Various tip loss corrections based on the Prandtl tip loss function are analysed in the article. Comparisons with measurements and theoretical analyses show that existing tip loss correction models are inconsistent and fail to predict correctly the physical behaviour in the proximity of the tip. A new tip loss correction model is proposed that remedies the inconsistency. Comparisons between numerical and experimental data show that the new model results in much better predictions of the loading in the tip region. Copyright © 2005 John Wiley & Sons, Ltd.

Tip studies using CFD and comparison with tip loss models

AbstractThe flow past a 95 kW Tellus rotor equipped with LM8·2 blades is computed using computational fluid dynamics for a standard tip and a swept tip. The difference in the near‐tip flow for the two tips for various tip speed ratios is examined and 3D airfoil data are extracted. The radial distribution of the averaged axial induction factor and the normal and tangential loads are compared with those of a standard blade element momentum code using 2D calibrated airfoil data for a wind speed of 9 m s−1, where the agreement in computed power is good. Further, a comparison with a new tip loss model proposed by Shen et al. has been performed for the same wind speed. Copyright © 2004 John Wiley & Sons, Ltd.

Catheter tip-associated granuloma: inflammatory mass with intrathecal drug delivery

Use of the intrathecal route to deliver drugs has become an acceptable treatment method for difficult pain syndromes. The primary advantage of intrathecal administration is the ability to deliver adequate relief at substantially lower doses of medication compared with other routes. This reduction of drug dosing leads to fewer side effects and improved efficacy. Morphine sulfate has been the most commonly used drug although other opioids and nonopioids have been prescribed. Over the past decade, the complication of an inflammatory mass at the catheter tip has been described. The prevalence of this problem appears to be much lower than 1%; however, because of the potential hazards, diagnostic vigilance is critical. Patient evaluation and reevaluation are the most important part aspect of the diagnosis. Loss of clinical efficacy, dermatomal pain in the distribution of the catheter tip, proprioceptive change, and sensory loss are early warnings. Motor loss, bladder and bowel dysfunction, and paralysis are late findings and occur with progression. When suspicion of the complication arises, a plain film should be obtained to identify the catheter tip, and then a T 1-weighted image should be performed at the tip. When magnetic resonance imaging (MRI) is not possible, a computerized tomography (CT) myelogram is an acceptable alternative. Treatment of this lesion involves discontinuing the infusion, then revising or removing the catheter. If spinal cord compression occurs, the treatment is direct surgical decompression. Many patients have continued with treatment after an inflammatory mass is diagnosed, once the catheter is revised or replaced. Prevention includes change of medications, avoidance of high-concentration morphine and hydromorphone, change of catheter tip location, and use of multiorifice catheters.

2.5-Dimensional Multi-Signal Large-Signal Analysis of Helix TWTs

A computer model (SUNRAY-3D) for the 2.5-dimensional multi-signal large-signal analysis of helix TWTs has been developed based on the approach developed earlier by the author for the one-dimensional large-signal modelling of helix and coupled-cavity TWTs. Some of the features of O'Malley's work for three-dimensional modelling of coupled-cavity TWTs were incorporated successfully for the modelling of helix TWTs. The present model is capable for the analysis of multiple input signals together with their higher order harmonics and inter-modulation products. The expressions for the circuit field and the induced current at a plane were derived from the electric field in a helical slow-wave structure instead of using the conventional equivalent circuit approach. The program analyses TWTs with arbitrary variations in the helix pitch and rf loss (including sever and tip loss) along the slow-wave structure. Induced backward voltage components and reflected voltage components due to mismatches at the terminations of the helix were included. The program has been shown to be accurate and self-consistent for drive powers from 60dB below saturation to well above saturation. The energy balance factor is satisfied to better than ±0.1% even at and above saturation. The CPU time to compute the performance of a typical TWT for a single drive power with 96 rings and 16 steps per wavelength is less than one minute on a DEC-ALPHA computer and is much less than 20 seconds on an IBM-P-IV.

후류영향을 고려한 상반회전 풍력발전 시스템의 공력성능 예측에 관한 연구

본 연구에서는 로터의 후류 효과 및 실속 후 특성을 고려하여 30kW급 상반회전 풍차 시스템에 대한 공력성능 해석을 수행하였다. 기본 공력이론은 모멘텀 이론과 2차원 준정상 공기력 이론을 통합한 형태를 사용하였다. 로터의 후류영향을 고려하기 위해 축소형 풍차 블레이드 모델에 대한 풍동시험 결과를 적절히 이용하였으며, 이로부터 보조로터를 지난 후류의 축속도 및 각속도 성분을 결정하였다. 또한, Glauert의 최적 작동판 이론과 Prandtl의 익단손실 효과를 고려하여 30kW급 풍차 시스템에 대한 최적 시위 및 비틀림 분포를 구하였으며, 기존의 단일 로터 시스템과의 공력성능 비교를 통하여 상반회전 풍차 시스템의 효율성 및 우수성을 입증하고자 하였다. In this paper, the aerodynamic performance prediction of a 30kW counter-rotating (C/R) wind turbine system has been made by using the momentum theory as well as the two-dimensional quasi-steady strip theory with special care on the wake and the post-stall effects. In order to take into account the wake effects in the performance analysis, the wind tunnel test data obtained for a scaled blade are used. Both the axial and rotational inductions behind the auxiliary rotors are determined through the wake model. In addition, the optimum chord and twist distributions along the blades are obtained from the Glauert's optimum actuator disk model considering the Prandtl's tip loss effect. The performance results of the counter-rotating wind turbine system are compared with those of the conventional single rotor system and demonstrated the effectiveness of the counter-rotating wind turbine system.

Interstitial Laser Therapy of Congenital VascularMalformations with MRI Guidance

Summary Introduction: Extratruncular, infiltrating congenital vascular malformations (CVM) are found in all organ systems. Large substance defects and diffuse blood loss may occur during surgical removal. Thus, conservative and interventional procedures are also applied, one of them being interstitial laser therapy (ILT). Patients and methods: Forty children with deep CVM underwent interstitial laser therapy with open MRI. The laser light guide was introduced into the malformation with a titan puncture needle and the tissue was thermically damaged by adequate selection of the physical parameters of the Nd:YAG 1064-nm laser. Beside the high soft-tissue contrast, MRI has the advantage of thermosensibility. For online thermomonitoring, we used 3 time-optimized MR sequences with a maximal velocity of 1 image in 3 seconds. Results: Positioning of the puncture needle was excellent in all applications and thermomonitoring was successful in 89%. A reduction of the tumor volume was observed in 36 patients at the 6-week follow-up. The volume of the malformations was reduced to 76%, on the average. Clinical improvement was seen in 78% of the cases. One fifth of the children are presently without symptoms. Thermic skin damage in 2 cases and intracorporal bare fiber tip loss in 1 case was found to be a complication. Discussion: Process control is decisive for successful interstitial laser therapy. Beside the high soft tissue contrast, MRI is characterized by a thermosensibility which does not allow invasive registration of temperature changes provoced by ILT inside the body. Summary: The introduction of open MR systems has enabled access to patients and interactive management directly in the magnetic field. MR-controlled interstitial laser therapy has to be included in the differential treatment of complicated congenital vascular malformations.

Aerodynamic optimisation of wings in multi-engined tractor propeller arrangements

Aerodynamic optimisation of wings in multi-engined tractor propeller arrangements is discussed and analysed with a fast calculation based on a Trefftz-plane analysis where the conservation laws of mass, momentum and energy are fulfilled in a control volume surrounding the configuration. The paper discusses the formulation of the optimisation algorithm based on augmented Lagrange integrals. The effect of viscous effects is incorporated in the calculation process. The method was implemented in a computer program which enables the user to find the optimum lift distribution for minimum drag for any tractor propeller/wing arrangement of arbitrary shape. As input for the slipstream data the user can either select input of experimental data or generate artificial data using a simple slipstream model based on the well-known blade element theory with Prandtl tip loss factor. Some numerical studies show that optimisation of a modern medium speed turboprop aircraft leads to performance increase by adapting the wing shape.

Performance of symmetric polygonal fins with and without tip loss — A comparison of different methods of prediction

AbstractNo analytical solution exists for estimating the efficiency of symmetric polygonal fins (SPFs) circumscribing circular tubes. Performance of such fins is conventionally determined from either of the two approximate techniques, namely, the equivalent annulus method and the sector method. The present work aims to judge the relative merits and applicability of these two methods critically. To this end, the results obtained from the approximate techniques have compared with those obtained from a semi‐analytical technique. It has been noted that, with the increase of the tip heat loss, the accuracy of prediction from any of the approximate methods decreases. For the sector method, a modification has been suggested. The prediction from the modified version of the sector method is always more accurate than that from the equivalent annulus method. It has been further illustrated that though the approximate techniques can be employed for the prediction of efficiency, they cannot be used to predict the tip temperatures accurately.

Preventing root tip loss in the maxillary sinus during endodontic surgery

Exclusion of infected root tips, dentinal debris, and inflammatory tissue from the maxillary sinus during endodontic surgery is imperative. A simple technique for preventing accidental root tip intrusion into the maxillary sinus using a 6-0 suture and needle and a hole prepared in the root tip with a #2 round bur prior to apicoectomy is presented.

Effect of an Unsteady Three‐Dimensional Wake on Elastic Blade‐Flapping Eigenvalues in Hover

This paper describes the formulation of a finite-state inflow model based on an acceleration potential and a helical wake geometry. The states of the model are coefficients of an inflow expansion in terms of a Fourier series (azimuthally) and of special polynomials (radially). The integrals over the wake are done in closed-form to obtain a set of ordinary differential equations for the inflow coefficients. The forcing functions for these equations are generalized forces which are integrals of the blade loading exactly as in structural dynamics. This model implicitly includes (for the hover case) Prandtl-Goldstein tip losses, dynamic inflow, and Theodorsen/Loewy lift deficiency. Thus, it is a fully three-dimensional unsteady wake model. Here, this model is coupled with elastic-blade equations in hover and eigenvalues are found. The results show that the three-dimensional wake has a large effect on the flap damping of all modes.

Experimental and numerical study of pattern formation in faceted cellular array growth

In this article, a review of our recent experimental and numerical study of pattern formation in faceted cellular array growth was presented.In situ observations in transparent faceting organic compounds have revealed the dynamical features of faceted cellular growth. Cell tip splitting and loss of cells in the array have been found to be the main mechanisms for cell spacing adjustment. The time evolution of a faceted cellular array has been followed numerically. It was found that pattern formation was history-dependent and was determined by interactions in the array. These interactions were either transient or persistent, depending on the growth condition. As a result, afinite range of stable cell spacings was found under a given growth condition; that is, there was no sharp selection. The cellular structures were irregular when persistent interactions occurred, whereas relatively regular structures could be formed once the transient interactions had stopped. The implication of these observations for pattern formation in other array growth processes, such as nonfaceted cellular, dendritic, or eutectic growth, will be discussed.

An analytical approach to optimum design and peak performance prediction for horizontal axis wind turbines

The existing methods for optimum design of horizontal axis wind turbine rotors either neglect the effects of drag and the finite number of blades or follow an iterative method to take these effects into account. The former method fails to predict the peak performance of the wind rotors. The latter method is cumbersome as it involves a multistage iterative process. A relationship between speed induction factors, drag/lift ratio and tip-loss factor has been derived corresponding to the maximum power extraction from horizontal axis wind turbines. Owing to the definite relationship, the optimum design and peak performance prediction method has been simplified, even when considering the effects of drag and tip losses. The analysis for design optimization, the design procedure and example cases are given. Results from the present method are compared with those from other published and widely accepted results.

Blade tip, finite aspect ratio, and dynamic stall effects on the Darrieus rotor

The objective of the work described in this paper was to apply the Boeing-Vertol dynamic stall model in an asymmetric manner to account for the asymmetry of the flow between the left and right sides of the rotor. This phenomenon has been observed by the flow visualization of a two-straight-bladed Darrieus rotor in the IMST water tunnel. Also introduced into the aerodynamic model are the effects of the blade tip and finite aspect ratio on the aerodynamic performance of the Darrieus wind turbine. These improvements are compatible with the double-multiple-streamtube model and have been included in the CARDAAV computer code for predicting the aerodynamic performance. Very good agreement has been observed between the test data (Sandia 17 m) and theoretical predictions; a significant improvement over the previous dynamic stall model was obtained for the rotor power at low tip speed ratios, while the inclusion of the finite aspect ratio effects enhances the prediction of the rotor power for high tip speed ratios. The tip losses and finite aspect ratio effects were also calculated for a small-scale vertical-axis wind turbine, with a two-straight-bladed (NACA 0015) rotor. 15 references.

Numerical solution of two- and three-dimensional rotor tip leakage models

Blade tip losses represent a major efficiency penalty in a turbine or compressor rotor. These losses are presently controlled by maintaining close tolerances on tip clearances. This paper initially focuses on the control of tip leakage flow through minimization of the discharge coefficient to control the normal leakage flow component. A detailed numerical study of rotor-tip winglets, using a two-dimensional (2-D) turbulent flow formulation in primitive variables, is reported. Long and short winglets on the pressure, suction, and both sides (partial shroud) of the blade tip are analyzed. The results of the viscous analysis indicate superior performance with a partial shroud. The numerical technique is extended further to incorporate the axial flow effects by solving the full three-dimensional (3-D) Navier-Stokes equations with tip clearance effects included in the analysis. The 3-D model is validated by comparing it with the experimental results of the double-sided discharge rig of an earlier investigation. In addition, the variations in the specification of the boundary conditions at the inlet and exit of the pressure and suction side channels are investigated in detail. Comparison of the numerical and experimental results suggests an improvement in the predictive capability of the 3-D model over the 2-D analysis. Nomenclature b = height of the channel CD = discharge coefficient Ckn = discharge coefficient for 2-D model (Ref. 9) D — dilation term du dv dw dx dy Lc = axial length of tip clearance slot (3-D model) Ld = axial length of blade downstream of tip clearance (3-D model) Lg =tip clearance, gap height (3-D model) Lp = width of pressure side channel (3-D model) Ls - width of suction side channel (3-D model)

Fingertip reconstruction with a palmar advancement flap and free dermal graft: A report of six cases

The palmar thumb advancement flap was first described by Moberg in 1964. It was further utilized for the thumb and defined by Posner and Smith in 1971. In 1980, Macht and Watson favorably reported their technique of palmar advancement that was applicable not only for the thumb, but also for all five digits with soft tissue tip losses. A further refinement of their technique is to augment the digital tip with an autogenous dermal graft. This dermal "padding" is placed directly over the bony tuft to act as a "shock absorber," add bulk and contour to the distal tip of the finger, increase soft tissue stability, eliminate direct percussive tenderness of the bone, and decrease disability for specific occupations such as those requiring typewriting. Six cases are reported.

Reconstruction Of The Thumb (Study of 100 Cases)

SummaryWe have evaluated 100 cases with particular emphasis on tip losses and total thumb loss. Various methods and follow up of partial thumb reconstruction and total thumb reconstruction are discussed.If necessary patients arve referred to physiotherapy and occupational therapy.We are thankful to Dr. B. R. Kalke, Dean. T. N. Medical College and B. Y. L. Nair Hospital, Bombay for his kind pernrission to use the hospital records and publish this paper.

Design and performance of a small shrouded cretan windwheel

A Cretan-type windwheel is attractive because of its design simplicity, low cost, durability and ease of construction by semi-skilled labour from a variety of indigenous materials. Utilising a 0·64 m diameter cycle wheel as the structurally strong framework for the windwheel sails provides a rotor that is sufficiently rigid, relatively cheap (especially if the wheel and axle are cannibalised from an abandoned bicycle) and readily available throughout the world. Sail manufacture, assembly and maintenance for a Cretan windwheel can usually be undertaken locally, so eliminating the high costs of importing commercially available wind energy conversion systems. Thus, Cretan-type windwheels are likely to be increasingly used in less developed countries despite their intrinsically poor capabilities for harnessing wind power. Test data for a shrouded version of the ‘cycle wheel’, Cretan system are presented. The use of nine loosely sheeted sails produced a maximum power output of 14 W for an air speed at entry to the rotor of 5 m s −1, corresponding to a free stream wind of less than 3·5 m s −1. For this system it was found that tight (rather than loose) sails harnessed relatively little power. The presence of the shroud, which reduced tip losses, led to higher power coefficients being attainable. Two possible applications for a larger version (than tested) shrouded, Cretan type windwheel are described, namely (i) for irrigation and land drainage in undeveloped countries and (ii) for stimulating a peristaltic pump which acts as a gravitational boost to drive solar-heated anti-freeze liquid around a low height, domestic central-heating circuit.