Harmonic Blade Research Articles

UHBR Open-Test Case Fan ECL5/CATANA: Non-Linear Analysis of Non-Synchronous Blade Vibration at Part-Speed Conditions

Abstract The onset of non-synchronous vibrations has been predicted for a composite open-test-case UHBR fan geometry by time-linearized simulations at part-speed conditions. In the current study, time-accurate simulations with harmonic blade oscillations have been conducted to investigate the non-linear behavior. Results for different operating conditions show the evolution of aeroelastic stability. The lock-in of convected aerodynamic disturbances with structural vibration is analyzed for different vibration amplitudes and frequencies. The simulations show the development of multiple wave numbers, mode scattering, and a non-linear dependency on vibration amplitude. The results indicate the possibility of limit-cycle prediction and the necessity of strongly coupled methods for the assessment of non-synchronous vibration.

Vibration analysis of a submarine elastic propeller-shaft-hull system using FRF-based substructuring method

A dynamic model to study the coupled longitudinal and transverse vibrations of a submarine elastic propeller-shaft-hull system is developed using the FRF-based substructuring method (FBSM). The total system is firstly modeled as two substructures: the elastic propeller-shaft subsystem and the hull shell. For the former substructure, the elastic propeller is modeled by using harmonic blade array elements and the shafts are assumed to be Timoshenko beams, while the latter one is modeled using traditional finite element method. After that, the two substructures are synthesized using FBSM. The modes, the natural frequencies and the coupled longitudinal and transverse vibration characteristics of the propeller-shaft subsystem, the hull shell, and the total system are analyzed. An experiment studying the dynamic characteristics of a large-scale submarine experimental setup is processed and compared with the numerical results, which shows great consistency. Finally, a further discussion is carried out focused on how the bearing stiffness affects the coupled vibration characteristics of the total system.

Flutter of long blades in a steam turbine

Cases of flutter appearing in the last stages of LP steam turbines have recently been reported. This paper presents a numerical analysis of flutter in the last stage of LP steam turbine blades using in-house, non-viscous and viscous codes as well as the ANSYS CFX viscous code. In the case of harmonic blade oscillations, instability regions were calculated using an aeroelastic damping coefficient for various interblade phase angles in five mode shapes. The distribution of this coefficient was also calculated along the blade length. It was found that flutter appears in the first mode shape. 3D viscous and non-viscous calculations showed that flutter appeared only in the first harmonic oscillation mode. In the other four modes, flutter did not appear. A negative aerodamping coefficient for the harmonic blade oscillations is not sufficient evidence of flutter. Conclusive evidence may be obtained using the two-way fluid–structure interaction procedure without assuming harmonic oscillation. In practice, the last stage LP rotor blades are mistuned and the pressure behind them is not uniform. Analysis of such conditions has to be done.

Modern methods for investigating the stability of a pitching floating platform wind turbine

Abstract. The QBlade implementation of the lifting-line free vortex wake (LLFVW) method was tested in conditions analogous to floating platform motion. Comparisons against two independent test cases using a variety of simulation methods show good agreement in thrust forces, rotor power, blade forces and rotor plane induction. Along with the many verifications already undertaken in the literature, it seems that the code performs solidly even in these challenging cases. Further to this, the key steps are presented from a new formulation of the instantaneous aerodynamic thrust damping of a wind turbine rotor. A test case with harmonic platform motion and collective blade pitch is used to demonstrate how combining such tools can lead to a better understanding of aeroelastic stability. A second case demonstrates a non-harmonic blade pitch manoeuvre showing the versatility of the instantaneous damping method.

Minimum Induced Power for a Rotor with a Finite Number of Blades

A dynamic inflow model is used to calculate minimum induced power for a helicopter in high-speed forward flight with a finite number of blades. Comparisons between analytical and numerical results are shown, and they show good agreement. Different flow conditions (such as with and without reverse flow or inflow feedback) are used to show how each condition affects optimum induced power. Several results confirm the findings of earlier investigations, such as a singularity in rotor power in reverse flow and induced power reduction with an increase in blade number. One of the new findings is that the induced power is affected by rotor solidity (in the absence of inflow feedback) and the effect of inflow feedback does not always reduce the induced power. Results obtained using higher harmonic blade pitch control show that induced power can thereby be reduced for all conditions with a finite number of blades.

Helicopter flight performance improvement by dynamic blade twist

Dynamic blade twist is investigated as a method for reducing rotor power and improving helicopter performance. An analytical model able to predict helicopter rotor power is first presented, and the flight data of the UH-60A helicopter and the Helicopter Multi-Block Method (HMB2) are used for validation. The predictions of the rotor power are in good agreement with the flight test data and HMB2, which verifies the application of the present method in analyzing helicopter performance. In hover and low speed forward flight, the power reduction by the prescribed dynamic blade twist is substantially small. In high speed forward flight, the effect of dynamic blade twist becomes more pronounced. It is found that lower harmonic blade twist can achieve larger power savings than higher harmonic twist. The zero harmonic twist dominates the power reductions. The helicopter take-off weight was found to have a strong influence on the power reductions achieved by the prescribed dynamic blade twist.

Flap-wise loads reduction of rotor blades by embedded flap-wise absorbers

ABSTRACTElastomeric and Fluidlastic®absorbers are proposed to be embedded in blade cavity to reduce troublesome second harmonic flap-wise blade loads of rigid rotors. A simple model of a blade with a flap-wise dynamic absorber is derived to investigate centrifugal force effects on the absorber's rotating frequency. The system's dynamic equations of motion indicate that centrifugal force has no effect on absorber's frequency under rotation. Aeroelastic simulation of the coupled rotor and absorber system based on an elastic beam model in generalised force formulation is used to explore load reduction extent and dynamic absorber behaviour. At a forward speed of 200 km/h, the elastomeric absorber reduces the second harmonic flap-wise root-bending moment by 88.8% for unacceptably large stroke; the Fluidlastic®absorber reduces the moment by 78.5% with a stroke 4.26% of blade chord length. Results indicate that placing an embedded Fluidlastic®absorber in the blade's flap-wise direction has potential for reducing load in different flight states with relatively small strokes. Increasing tuning port area ratio or Fluidlastic®absorber mass can distinctly decrease strokes without increasing loads. However, deviation from normal rotor speed significantly lowers Fluidlastic®absorber performance.

An assessment of using variable blade pitch for moored ocean current turbine flight control

This paper investigates the possibility of using active individual blade pitch control for positioning moored ocean current turbines within an array. Using a numerical simulation of a representative ocean current turbine it is shown that harmonic blade oscillations with amplitudes of 1.5° can be used to displace an ocean current turbine laterally by a distance equal to one rotor diameter, when the mooring cable length is approximately 30 times the diameter of the rotor blade. For current flow directions that would result in a downstream turbine operating in the wake of an upstream system at a distance of 10 diameters, this technique could be used to reduce the power loss of the downstream system from about 50% (caused by the reduced flow speed available in the turbine wake) to the 1.2% power loss associated with the suggested control approach.

Acute and subacute effects of the ultrasonic blade and electrosurgery on nerve physiology

Ultrasonic blades have been shown to cause less acute electrophysiological damage when applied near nerves than monopolar electrosurgery (ES). This study was performed to determine whether the acute nerve damage observed for ES, as well as the relative lack of damage observed for ultrasonic dissection, extends through a subacute timeframe. Muscle incisions were made in rat with the Harmonic® Blade (HB) and ES at a distance of 2 mm from the sciatic nerve. Sham surgery was also performed which consisted of similar exposure of the sciatic nerve without use of an energized device. Electrophysiological function was assessed acutely over a 3-h period, and subacutely after a 7-day survival, by monitoring the sciatic nerve compound action potential (CAP), conduction velocity (CV), von Frey hair (VFH) stimulation force, leukocyte infiltration, and impaired axonal transport via β-amyloid precursor protein (β-APP) immunocytochemistry.During the acute period, ES produced significantly lower CAP and CV, and higher levels of leukocytes and β-APP than sham, whereas the ultrasonic blade was not significantly different from sham, and had significantly lower VFH force than ES. After the subacute survival, ES continued to display significantly lower CAP and CV, and higher levels of leukocytes and β-APP than sham, whereas ultrasonic blade had higher CAP and CV than sham, and lower VFH than ES. This study confirms that incisions made with an ultrasonic blade cause less acute nerve damage than monopolar ES, and are comparable to sham surgery at a distance of 2 mm from the sciatic nerve. The negative effects of electrosurgery extend through at least a 7-day survival period, whereas subacute recovery after application of the ultrasonic blade was comparable to that of sham surgery. For surgical procedures in the vicinity of vital nerves, use of the ultrasonic blade represents a lower risk than ES for both acute and subacute neural trauma.

Parallel Blade-Vortex Interaction Modelling for Helicopter Rotor Noise Control Synthesis

The present work deals with a methodology for the alleviation of loads and corresponding emitted noise generated by blade-vortex interaction (BVI) phenomena occurring on helicopter main rotors in low-speed, descent flight. It consists of a multi-cyclic, optimal control approach driving higher harmonic blade pitch actuation. First, for the specific flight condition to be examined, the BVI phenomena are simulated as equivalent two-dimensional, multi-vortex, parallel BVI problems and then a local controller methodology is applied for the efficient identification of the closed-loop control algorithm. In order to assess the capability of the proposed control approach to alleviate rotor blade loads and emitted noise, the results of a numerical investigation concerning a realistic helicopter main rotor in descent flight are presented and discussed.

Use of the Harmonic Blade Scalpel as a Novel Technique for Thoracoscopic Resection of Pediatric Paraspinal Masses in Children

Data support use of video-assisted thoracoscopic surgery (VATS) for safe and effective resection of paraspinal masses in children. Our aim was to describe outcomes following this operation using a novel technique and to compare its use with that of other established techniques. We performed a retrospective chart review of all children (<18 years old) undergoing thoracoscopic resection of paraspinal masses in 2000-2011. Demographics, operative details, and clinical outcomes were summarized and compared between those undergoing resection using a Harmonic (Ethicon Endo-Surgery, Blue Ash, OH) blade scalpel (HBS) and those who did not. Sixteen cases were identified (median age, 57.5 months; range, 2-204 months). Six cases (37%) underwent VATS with use of the HBS, and 10 (63%) did not. Demographic and clinical factors were well matched. Median tumor diameter was larger in the HBS group (49.2 cm(3) versus 18.7 cm(3); P=.07). Operative time was similar between groups (121 versus 138 minutes; P=.25), as was the estimated blood loss (10 mL versus 30 mL; P=.91) and chest tube duration (2.1 versus 1.8 days; P=.78). Three cases of Horner's syndrome developed in the standard resection group, and one complication occurred in the HBS group. The Harmonic blade scalpel can be used as a simple alternative to standard dissection techniques for thoracoscopic resection of paraspinal masses in children.

The HART II international workshop: an assessment of the state of the art in CFD/CSD prediction

Over the past decade, there have been significant advancements in the accuracy of rotor aeroelastic simulations with the application of computational fluid dynamics methods coupled with computational structural dynamics codes (CFD/CSD). The HART II international workshop database, which includes descent operating conditions with strong blade–vortex interactions (BVI), provides a unique opportunity to assess the ability of CFD/CSD to capture these physics. In addition to a baseline case with BVI, two additional cases with 3/rev higher harmonic blade root pitch control are available for comparison. The collaboration during the workshop permits assessment of structured, unstructured, and hybrid overset CFD/CSD methods from across the globe on the dynamics, aerodynamics, and wake structure. Evaluation of the plethora of CFD/CSD methods indicates that the most important numerical variables associated with most accurately capturing BVI include the use of either a two-equation RANS model or detached eddy simulation-based turbulence model and a sufficiently small time step. An appropriate trade-off between grid fidelity and spatial accuracy schemes also appears to be important for capturing BVI on the advancing side of the rotor disk. Overall, the CFD/CSD methods generally fall within the same accuracy; cost-effective hybrid Navier-Stokes/Lagrangian wake methods tend to correlate less accurately with experiment and have larger data scatter than the full CFD/CSD methods for most parameters evaluated. The importance of modeling the fuselage is observed, and other requirements are discussed.

The HART II international workshop: an assessment of the state-of-the-art in comprehensive code prediction

Significant advancements in computational fluid dynamics (CFD) and their coupling with computational structural dynamics (CSD, or comprehensive codes) for rotorcraft applications have been achieved recently. Despite this, CSD codes with their engineering level of modeling the rotor blade dynamics, the unsteady sectional aerodynamics and the vortical wake are still the workhorse for the majority of applications. This is especially true when a large number of parameter variations is to be performed and their impact on performance, structural loads, vibration and noise is to be judged in an approximate yet reliable and as accurate as possible manner. In this article, the capabilities of such codes are evaluated using the HART II International Workshop database, focusing on a typical descent operating condition which includes strong blade–vortex interactions. A companion article addresses the CFD/CSD coupled approach. Three cases are of interest: the baseline case and two cases with 3/rev higher harmonic blade root pitch control (HHC) with different control phases employed. One setting is for minimum blade–vortex interaction noise radiation and the other one for minimum vibration generation. The challenge is to correctly predict the wake physics—especially for the cases with HHC—and all the dynamics, aerodynamics, modifications of the wake structure and the aero-acoustics coming with it. It is observed that the comprehensive codes used today have a surprisingly good predictive capability when they appropriately account for all of the physics involved. The minimum requirements to obtain these results are outlined.

Numerical simulation of clocking effect on blade unsteady aerodynamic force in axial turbine

To give an insight into the clocking effect and its influence on the wake transportation and its interaction, the unsteady three-dimensional flow through a 1.5-stage axial low pressure turbine is simulated numerically by using a density-correction based, Reynolds-Averaged Navier-Stokes equations commercial CFD code. The 2nd stator clocking is applied over ten equal tangential positions. The results show that the harmonic blade number ratio is an important factor affecting the clocking effect. The clocking effect has very small influence on the turbine efficiency in this investigation. The difference between the maximum and minimum efficiency is about 0.1%. The maximum efficiency can be achieved when the 1st stator wake enters the 2nd stator passage near blade suction surface and its adjacent wake passes through the 2nd stator passage close to blade pressure surface. The minimum efficiency appears if the 1st stator wake impinges upon the leading edge of the 2nd stator and its adjacent wake of the 1st stator passes through the mid-channel in the 2nd stator. The wake convective transportation and the blade circulation variation due to its impingement on the subsequent blade are the main mechanism affecting the pressure variation in blade surface.

The effects of ultrasonic and electrosurgery devices on nerve physiology

Background. While the risks associated with the use of electrosurgery near nerves are well known, few studies have examined the neurophysiologic effects of application of the Harmonic Blade, an ultrasonic scalpel, in the vicinity of nerve fibres. This study sought to compare the sub-acute neurophysiologic effects of the Harmonic Blade and electrosurgery after incisions close to the sciatic nerve. Methods. Incisions were made in rats with the Harmonic Blade and electrosurgery at distances of 1, 2, 3 and 4 mm from the sciatic nerve. Sham surgery was also performed. The compound action potential, conduction velocity and calibrated nylon filament (von Frey hair, VFH) stimulating force were monitored for up to 3 hours after surgery. The sciatic nerve was assessed for inflammation via H&E staining and impaired axonal transport by β-APP immunohistochemistry. Results. Electrosurgery incisions produced a significantly greater decrease in compound action potential and conduction velocity, and increase in the VFH force than the Harmonic Blade over all time points and distances from the sciatic nerve. The Harmonic Blade was similar to sham surgery for the compound action potential and VFH force. Electrosurgery yielded significantly greater leukocyte infiltration than the Harmonic Blade and produced the highest levels of β-APP immunoreactive swellings. Conclusions. Incisions with electrosurgery in the range of 1–4 mm of the sciatic nerve caused substantial changes in neurophysiologic functioning and inflammation. In contrast, the Harmonic Blade was similar to sham surgery in the vicinity of the nerve, producing little observable acute trauma.

Use of an Ultrasonic Blade Facilitates Muscle Repair After Incision Injury

The ultrasonic Harmonic Blade cuts and coagulates soft tissue at temperatures lower than conventional electrosurgery. This study investigated whether improved hemostatic control and reduced collateral damage in skeletal muscle incisions translates into improved myofiber regeneration, reduced fibrosis and faster muscle recovery. Transections in the left gastrocnemius muscles of mice were made with the Harmonic Blade, and contralaterally, with either cold steel scissors or electrosurgery. Histology up to 8 wk after surgery was performed to evaluate myofiber regeneration and fibrosis. Tissue inflammation (Gr1+ neutrophils) and vascularization (CD31+ capillaries) were assessed immunohistochemically at 1 wk . Overall the Harmonic Blade showed significantly higher level of muscle regeneration than cold steel. Fibrosis for both the Harmonic Blade and cold steel decreased three-fold over the 8 wk period, whileelectrosurgery yielded significantly increasing fibrosis through wk 4 before declining. At 1 wk post-surgery the Harmonic Blade induced less inflammation than electrosurgery, and higher vascularization than electrosurgery and cold steel. Harmonic Blade-incised tissue showed accelerated vascularization, slight reduction of inflammation, enhanced muscle regeneration and decreased scarring, demonstrating a more effective healing process than electrosurgery.

Use of the Harmonic Blade in Face Lifting: A Report Based on 420 Operations

Use of the Harmonic Blade in Face Lifting: A Report Based on 420 Operations

Healing of Iatrogenic Skeletal Muscle Wounds Is Affected by Incision Device

Orthopedic joint procedures frequently require extensive dissection of skeletal muscles resulting in tissue injury, formation of scar tissue, pain, and potentially, functional impairment. The authors hypothesized that using a low-temperature ultrasonic cutting and coagulating device (Harmonic Blade, Ethicon Endo-Surgery, Cincinnati, OH) would result in reduction in tissue trauma in terms of reducing acute and chronic inflammation during healing. Bilateral longitudinal incisions were made into the tibialis cranialis muscles of rabbits with either a Harmonic Blade or a standard monopolar electrosurgical scalpel. At 3, 7, and 21 days postoperatively, necropsy and histological evaluations indicated a significant attenuation of acute inflammation (P = .011) for the Harmonic incisions compared with electrosurgery. No significant differences were observed for chronic inflammation, necrosis, or fibrosis. Use of a Harmonic scalpel during dissection of skeletal muscle in orthopedic surgery may result in reduced influx of neutrophils, reducing acute inflammation, and potentially aid in reducing postoperative pain and functional impairment.

Use of the Harmonic Blade in Face Lifting: A Report Based on 420 Operations

An important concern for patients who undergo a face lift is the recovery time. Use of the Harmonic blade (Ethicon Endo-Surgery, Cincinnati, Ohio) for surgical dissection and hemostasis in face lift has improved recovery time and greatly reduced the risk of hematomas in the senior author's practice. A retrospective study evaluated the complication rate using the Harmonic blade in face and neck lifting (n = 420) between 2001 and 2007. A prospective study was conducted on 100 cases (October of 2006 to May of 2008) to evaluate the mean operative time, drainage, and recovery time. Results at day 8 were evaluated using on a scale of 1 to 4 (1 = nil tracking to 4 = marked tracking). The complication rate in 420 cases was low and decreased with experience. Complications included hematoma (n = 5), temporary facial paresis (n = 4), submental lipolysis (n = 3), skin perforation (n = 1), minor skin burn (n = 1), skin necrosis (n = 0), and hair loss (n = 0). Mean operative time for face lift with a superficial musculoaponeurotic system procedure and anterior platysmaplasty was 180 minutes (range, 140 to 210 minutes). Drainage at day 1 was 20 cc (range, 0 to 30 cc). Average return to normal social life was by day 8 (range, 5 to 20 days). Results at day 8 were graded 1 for edema and ecchymosis. The beneficial effects of the Harmonic blade are obvious objectively and subjectively to both the surgeon and the patients. Understanding the key technical details involved with its use will improve the learning curve for the surgeon as this technology becomes an asset in face lifting.

Lifting surface theory to predict aerodynamic forces induced by oscillating blades under interaction of three bladerows

The paper presents the unsteady lifting surface theory to predict unsteady aerodynamic forces on blades of aerodynamically coupled three annular bladerows. Blades of any one bladerow are assumed to be vibrating. The bladerows are assumed to be individually rotating with arbitrary rotational velocities, and therefore the model can be reduced to a rotor/stator/rotor model or a counter-rotating multi-rotor system model by appropriately specifying rotational velocity parameters. The details of the mathematical formulations and the solution procedures are described. Numerical studies were conducted. The disturbances produced by a simple harmonic blade vibration are composed of multiple frequency components because of aerodynamic interaction between bladerows in mutual rotational motions. Relative magnitudes of the frequency components of the unsteady aerodynamic forces are made clear. Not only the effects of nonoscillating neighboring bladerows on the unsteady aerodynamic response of the oscillating bladerow, but also the unsteady aerodynamic forces on nonoscillating neighboring bladerows induced by the oscillating bladerow are investigated.