Asymmetric Pressure Research Articles

Theoretical analysis and simulation of obstructed breakup of micro-droplet in T-junction under an asymmetric pressure difference

Asymmetric droplet breakup under a pressure difference at two outlets of a T-junction is investigated theoretically and numerically in this study. An accurate analysis of the evolution of droplet dynamics during the obstructed breakup process has been conducted. Meanwhile, the lattice Boltzmann method based on color gradient model is employed to simulate the system with the verification of the theoretical results. It is demonstrated that the Zou-He boundary setting at each outlet is advantageous for modifying the pressure drop of the two branches of T-junction. The results reveal that asymmetric breakup of the unequally sized droplets follows two steps, namely, the filling stage and the breakup stage. Then a universal parameter is proposed to describe the asymmetric condition of droplet breakup in T-junction, which plays a key role to characterize the temporal evolution of volume ratio and the droplet length of formed smaller droplets.

Experimental Investigation of Pressure Fluctuations on Inner Wall of a Centrifugal Pump

Abstract Affected by rotor–stator interaction and unstable inner flow, asymmetric pressure distributions and pressure fluctuations cannot be avoided in centrifugal pumps. To study the pressure distributions on volute and front casing walls, dynamic pressure tests are carried out on a centrifugal pump. Frequency spectrum analysis of pressure fluctuation is presented based on Fast Fourier transform and steady pressure distribution is obtained based on time-average method. The results show that amplitudes of pressure fluctuation and blade-passing frequency are sensitive to the flow rate. At low flow rates, high-pressure region and large pressure gradients near the volute tongue are observed, and the main factors contributing to the pressure fluctuation are fluctuations in blade-passing frequency and high-frequency fluctuations. By contrast, at high flow rates, fluctuations of rotating-frequency and low frequencies are the main contributors to pressure fluctuation. Moreover, at low flow rates, pressure near volute tongue increases rapidly at first and thereafter increases slowly, whereas at high flow rates, pressure decreases sharply. Asymmetries are observed in the pressure distributions on both volute and front casing walls. With increasing of flow rate, both asymmetries in the pressure distributions and magnitude of the pressure decrease.

New insights on tuberculous aortitis

ObjectiveAortitis is an exceedingly rare manifestation of tuberculosis. We describe 11 patients with tuberculous aortitis (TA). MethodsMulticenter medical charts of patients hospitalized between 2003 and 2015 with TA in Paris, France, were reviewed. Demographic, medical history, laboratory, imaging, pathologic findings, treatment, and follow-up data were extracted from medical records. TA was considered when aortitis was diagnosed in a patient with active tuberculosis. ResultsEleven patients (8 women; median age, 44.6 years) with TA were identified during this 12-year period. No patient had human immunodeficiency virus infection. Tuberculosis was active in all cases, with a median delay of 18 months between the first symptoms and diagnosis. At disease onset, vascular signs were mainly claudication, asymmetric blood pressure, and diminished distal pulses. Constitutional symptoms or extravascular signs were present in all patients at some point. Aortic pseudoaneurysm was the most frequent lesion, but three patients had isolated inflammatory aortic stenosis. TA appeared as extension from a contiguous infection in only three cases. Tuberculosis was considered because of clinical features, tuberculin skin or QuantiFERON-TB Gold (Quest Diagnostics, Madison, NJ) test results, pathologic findings, and improvement on antituberculosis therapy. A definite Mycobacterium tuberculosis identification was made in only three cases. All patients received antituberculosis therapy for 6 to 12 months. Surgery including Bentall procedures, aortic bypass, and open abdominal aneurysm repair was performed at diagnosis in eight patients. Seven patients received steroids as an adjunct therapy. All patients clinically improved under treatment. No patients died for a median follow-up duration of 4 years. ConclusionsTA may result in aneurysms contiguous to regional adenitis but also in isolated inflammatory aortic stenosis. Steroids may be associated with antituberculosis therapy for inflammatory stenotic lesions. Surgery is indicated for aneurysms and in case of worsening stenotic lesions despite anti-inflammatory drugs. No patient died after such combined treatment strategy.

Pharyngeal swallowing pressures in the base-of-tongue and hypopharynx regions identified with three-dimensional manometry.

This study aims to use three-dimensional (3D) high-resolution manometry to identify circumferential pressure patterns generated within the asymmetrical base-of-tongue and hypopharynx regions of the pharynx during deglutition. Case series. Radial pressures in the regions of interest were evaluated during swallowing events in 12 healthy subjects using 3D high-resolution manometry. Repeated measures analysis of variance revealed asymmetrical pharyngeal clearance pressures in the base-of-tongue and hypopharynx regions during swallowing. A significant main effect of direction on pressure was found at the time point of average maximum pressure (P < 0.001) and for pressure integral (P < 0.001), with pressure primarily generated from the posterior direction. An interaction was noted between direction and location when comparing maximum directional pressures, regardless of time (P =0.045), highlighting the differences in anterior pressure production between regions. In contrast to the high posterior pressures produced in the base-of-tongue region, an anteroposterior dominant pressure pattern was observed in the hypopharynx. Pressure waveform complexity in the hypopharynx also is likely attributed to activity in the anterior and posterior directions. Symmetrical pressure generation was observed during intrabolus flow within the hypopharynx. This study shows that pressure is asymmetrically generated in the base-of-tongue and hypopharynx regions during swallowing of a 10-mL bolus, reflecting the complex anatomy within the pharynx. Understanding of these complex pressure patterns aids in the interpretation of high-resolution manometry and can help guide further study in the clinical assessment and treatment of pharyngeal pathology. 4. Laryngoscope, 127:1989-1995, 2017.

Aeroelastic and aerodynamic interference effects on a high-rise building

The 492m high Shanghai World Financial Centre is an interesting high-rise building in that the cross-section varies with the height. It is surrounded by a number of other buildings, including some of about half the height of it, a slightly lower nearby Jin Mao building, and a higher Shanghai Centre (not considered here). A series of wind tunnel tests for aeroelastic model vibration measurement and rigid model pressure measurement were carried out to investigate the aeroelasticity and aerodynamic interference effects on this building. The results show that, the densely clustered high-rise buildings (excluding the Jin Mao building) located upstream may cause the mean positive pressures of the lower obscured surface of the World Financial Centre to decrease, and the RMS pressures to increase or decrease for different configuration, which would exert some influences on the average and RMS responses. When buildings are located downstream, the wind-induced aerodynamic interference is negligible. When the Jin Mao building lies upstream, the mean positive pressures on the obscured surface of the World Financial Centre would decrease and even may become negative (the maximum absolute values may increase obviously), and the RMS pressures may also increase significantly, which cause the average displacement responses along-wind to reduce, the RMS horizontal displacement responses to increase, and the rotational displacement responses to increase for asymmetrical pressure. Moreover, it will weaken the energy and periodicity of vortex shedding of the World Financial Centre so as to reduce the possibility or amplitude of vortex resonance. More specifically, when the Jin Mao building lies downstream, the interference effects of the wind loads and wind-induced vibration of rigid World Financial Centre are less obvious, however, when the aeroelasticity is considered at the same time, a significant vortex resonance arose in the direction along the first order modal of the World Financial Centre at a lower wind speed, for which the natural frequency is close to the vortex shedding frequency. The findings derived from the present study are believed to be useful to gain further insight into the aeroelasticity and aerodynamic interference effects of high-rise buildings.

Modes of reaction front propagation and end-gas combustion of hydrogen/air mixtures in a closed chamber

Modes of reaction front propagation and end-gas combustion of hydrogen/air mixtures in a closed chamber are numerically investigated using an 1-D unsteady, shock-capturing, compressible and reacting flow solver. Different combinations of reaction front propagation and end-gas combustion modes are observed, i.e., 1) deflagration without end-gas combustion, 2) deflagration to end-gas autoignition, 3) deflagration to end-gas detonation, 4) developing or developed detonation, occurring in the sequence of increasing initial temperatures. Effects of ignition location and chamber size are evaluated: the asymmetric ignition is found to promote the reactivity of unburnt mixture compared to ignitions at center/wall, due to additional heating from asymmetric pressure waves. End-gas combustion occurs earlier in smaller chambers, where end-gas temperature rise due to compression heating from the deflagration is faster. According to the ξ−ε regime diagram based on Zeldovich theory, modes of reaction front propagation are primarily determined by reactivity gradients introduced by initial ignition, while modes of end-gas combustion are influenced by the total amount of unburnt mixture at the time when autoignition occurs. A transient reactivity gradient method is provided and able to capture the occurrence of detonation.

CFD Simulations of a Finned Projectile with Microflaps for Flow Control

This research describes a computational study undertaken to determine the effect of a flow control mechanism and its associated aerodynamics for a finned projectile. The flow control system consists of small microflaps located between the rear fins of the projectile. These small microflaps alter the flow field in the aft finned region of the projectile, create asymmetric pressure distributions, and thus produce aerodynamic control forces and moments. A number of different geometric parameters, microflap locations, and the number of microflaps were varied in an attempt to maximize the control authority generated by the flaps. Steady-state Navier-Stokes computations were performed to obtain the control aerodynamic forces and moments associated with the microflaps. These results were used to optimize the control authority at a supersonic speed,M=2.5. Computed results showed not only the microflaps to be effective at this speed, but also configurations with 6 and 8 microflaps were found to generate 25%–50% more control force than a baseline 4-flap configuration. These results led to a new optimized 8-flap configuration that was further investigated for a range of Mach numbers fromM=0.8to5.0and was found to be a viable configuration effective in providing control at all of these speeds.

Propagation of Cracks in the Secondary Lining of Tunnels Subjected to Asymmetrical Pressure and a Safety Evaluation

This paper aims to study the way cracks propagate in the secondary lining of tunnels subjected to asymmetrical pressure and to determine the corresponding safety evaluation standards. To achieve this, a cracked part of the secondary lining of the Gucheng-Zhuxi expressway tunnel in Hubei, China was studied under asymmetrical pressure. Using fracture mechanics, the propagation laws and characteristics of the cracks on different scales are analyzed under different asymmetrical pressures and at different positions. The study is based on stress-intensity factor theory and uses ANSYS finite-element software. The results show that crack width (b) has a small effect on crack propagation in the lining structure. On the other hand, crack depth (h) has an obvious effect. The stress-intensity factors at asymmetrically-loaded positions are found to be clearly larger than those at symmetrically-loaded positions. That is, an asymmetrical pressure distribution promotes the propagation of cracks at asymmetrically-loaded positions (and inhibits that at symmetrically-loaded positions, to some extent). When the value of h falls in the range from 3 to 12 cm, the cracks propagate in a stable manner in asymmetrically-loaded positions; at a depth of 15 cm, the propagation becomes unstable. Thus, a crack depth of h = 12 cm can be regarded as the critical value signaling the onset of instability and failure of the secondary lining when considering the safety margin required of the lining structure. Combining the existing safety evaluation standards for cracks with a new evaluation index—the crack depth h—we propose a new safety evaluation standard that is suitable for cracks in the secondary lining of the Gucheng-Zhuxi expressway tunnel under asymmetrical pressure. In addition, suggestions are made for properly treating different types of crack.

Imbalanced positive selection maintains the functional divergence of duplicated DIHYDROKAEMPFEROL 4-REDUCTASE genes.

Gene duplication could be beneficial by functional division but might increase the risk of genetic load. The dynamics of duplicated paralogs number could involve recombination, positive selection, and functional divergence. Duplication of DIHYDROFLAVONOL 4-REDUCTASE (DFR) has been reported in several organisms and may have been retained by escape from adaptive conflict (EAC). In this study, we screened the angiosperm DFR gene focusing on a diversified genus Scutellaria to investigate how these duplicated genes are retained. We deduced that gene duplication involved multiple independent events in angiosperms, but the duplication of DFR was before the divergence of Scutellaria. Asymmetric positive selective pressures resulted in different evolutionary rates between the duplicates. Different numbers of regulatory elements, differential codon usages, radical amino acid changes, and differential gene expressions provide evidences of functional divergence between the two DFR duplicates in Scutellaria, implying adaptive subfunctionalization between duplicates. The discovery of pseudogenes accompanying a reduced replacement rate in one DFR paralogous gene suggested possibly leading to “loss of function” due to dosage imbalance after the transient adaptive subfunctionalization in the early stage of duplication. Notwithstanding, episodic gene duplication and functional divergence may be relevant to the diversification of ecological function of DFR gene in Scutellaria.

Evolution of directional hearing in moths via conversion of bat detection devices to asymmetric pressure gradient receivers

Small animals typically localize sound sources by means of complex internal connections and baffles that effectively increase time or intensity differences between the two ears. However, some miniature acoustic species achieve directional hearing without such devices, indicating that other mechanisms have evolved. Using 3D laser vibrometry to measure tympanum deflection, we show that female lesser waxmoths (Achroia grisella) can orient toward the 100-kHz male song, because each ear functions independently as an asymmetric pressure gradient receiver that responds sharply to high-frequency sound arriving from an azimuth angle 30° contralateral to the animal's midline. We found that females presented with a song stimulus while running on a locomotion compensation sphere follow a trajectory 20°-40° to the left or right of the stimulus heading but not directly toward it, movement consistent with the tympanum deflections and suggestive of a monaural mechanism of auditory tracking. Moreover, females losing their track typically regain it by auditory scanning-sudden, wide deviations in their heading-and females initially facing away from the stimulus quickly change their general heading toward it, orientation indicating superior ability to resolve the front-rear ambiguity in source location. X-ray computer-aided tomography (CT) scans of the moths did not reveal any internal coupling between the two ears, confirming that an acoustic insect can localize a sound source based solely on the distinct features of each ear.

Numerical Investigation of the Dynamic Characteristics of a Dual-Throat-Nozzle for Fluidic Thrust-Vectoring

A computational method tailored for the simulation of fluidic thrust-vectoring systems is employed to investigate the dynamic response of a dual-throat nozzle in open- and closed-loop control. Thrust vectoring in fixed, symmetric nozzles is obtained by secondary flow injections that cause local flow separations, asymmetric pressure distributions, and, as a consequence, the vectoring of primary jet flow. The computational technique is based on a well-assessed mathematical model for the compressible unsteady Reynolds-averaged Navier–Stokes equations. A minimal control system governs the unsteady blowing. Nozzle performances and thrust-vector angles have been computed for a wide range of nozzle pressure ratios and secondary flow injection rates. The numerical results are compared with the experimental data available in the open literature. Several computations of the open-loop dynamics of the nozzle under different forcing have been performed to investigate the system response in terms of thrust-vectoring effectiveness and controllability. These computations have been used to extract autoregressive exogenous models of the nozzle dynamics. The effects of including the actuator dynamics are also discussed. Simple strategies of closed-loop control of the nozzle system by proportional–integrative–derivative regulators are investigated numerically. The closed-loop model predictive control of the system, based on the autoregressive exogenous models, is addressed.

Changes in the Choroidal Thickness and Axial Length Upon Mannitol Infusion in Patients With Asymmetric Intraocular Pressure.

To evaluate the changes in the choroidal thickness (CT) and axial length (AL) upon systemic mannitol infusion in glaucoma patients with asymmetric intraocular pressure (IOP). Forty glaucoma patients with asymmetric IOP, with the IOP of 1 eye ≥40 mm Hg and the fellow eye <25 mm Hg, were administered 150 mL of a 20% mannitol infusion to reduce the IOP. The CT and AL were measured before and an hour after the infusion. The relationship between the IOP reduction and the changes in the CT and AL were investigated. The mean decrease in the IOP was -14.23 mm Hg (32.15%) and -4.13 mm Hg (21.40%) in the eyes with higher IOP and their fellow eyes, respectively. The mean changes in the subfoveal CT were 19.28 µm (9.20%; P<0.001) and 2.60 µm (1.93%; P=0.452) in the eyes with higher IOP and their fellow eyes, respectively. The mean changes in the AL were -0.10 µm (0.42%; P<0.001) and -0.33 mm (0.14%; P=0.008) in the eyes with higher IOP and their fellow eyes, respectively. Stepwise analysis revealed that the percent IOP change is the most influential factor on the percent change of the subfoveal CT (P<0.0001; R=0.3). These results suggest that large IOP changes upon mannitol infusion cause the shortening of the AL in both the eyes and the thickening of the choroid only in the eyes with a higher IOP.

Thermal diode in gas-filled nanogap with heterogeneous surfaces using nonequilibrium molecular dynamics simulation

A thermal diode serves as a basic building block to design advanced thermal management systems in energy-saving applications. However, the main challenges of existing thermal diodes are poor steady-state performance, slow transient response, and/or extremely difficult manufacturing. In this study, the thermal diode is examined by employing an argon gas-filled nanogap with heterogeneous surfaces in the Knudsen regime, using nonequilibrium molecular dynamics simulation. The asymmetric gas pressure and thermal accommodation coefficients changes are found due to asymmetric adsorptions onto the heterogeneous nanogap with respect to the different temperature gradient directions, and these in turn result in the thermal diode. The maximum degree of diode (or rectification) is Rmax ∼ 7, at the effective gas-solid interaction ratio between the two surfaces of ε* = 0.75. This work could pave the way to designing advanced thermal management systems such as thermal switches (transistors).

Short Helical Combustor: Dynamic Flow Analysis in a Combustion System With Angular Air Supply

A novel gas turbine combustor is investigated by means of a global flow analysis. Its main feature is the helical arrangement of the burners, which allows the utilization of the high angular momentum of the flow from compressor, so that the length of the flame tube and the number of NGV can be reduced. The concept was studied in Ariatabar et al. (2016, “Short Helical Combustor: Concept Study of an Innovative Gas Turbine Combustor With Angular Air Supply,” ASME J. Eng. Gas Turbines Power, 138(3), p. 031503) based on similarity considerations and a kinematic assessment of the simulated flow in various combustor models. For the best configuration found in the previous work, the exit mean flow angle was lower than the half of its initial value at the combustor inlet. The reason for this unwanted decay of the initial high angular momentum flux was not clear. In the present work, the underlying physics of the strong reduction of the mean flow angle is elucidated by analysis of the integral balance equation of angular momentum. It is shown that the flow in the vicinity of the burners is governed by inertial forces associated with an asymmetric pressure distribution on the sidewall and the combustor dome. The friction and turbulent mixing phenomena are found to have marginal effects on the flow pattern. To compare mean flow quantities of different combustor designs, a physically consistent averaging method is introduced, which can also be applied to a conventional combustor to assess different swirl configurations regarding the resulting flow pattern, mixing performance, and total pressure loss.

Determinants and prognostic implications of the negative diastolic pulmonary pressure gradient in patients with pulmonary hypertension due to left heart disease.

The diastolic pulmonary pressure gradient (DPG) has recently been introduced as a specific marker of combined pre-capillary pulmonary hypertension (Cpc-PH) in left heart disease (LHD). However, its diagnostic and prognostic superiority compared with traditional haemodynamic indices has been challenged lately. Current recommendations explicitly denote that in the normal heart, DPG values are greater than zero, with DPG ≥7 mmHg indicating Cpc-PH. However, clinicians are perplexed by the frequent observation of DPG <0 mmHg (DPGNEG ), as its physiological explanation and clinical impact are unclear to date. We hypothesized that large V-waves in the pulmonary artery wedge pressure (PAWP) curve yielding asymmetric pressure transmission might account for DPGNEG and undertook this study to clarify the physiological and prognostic implications of DPGNEG . Right heart catheterization and echocardiography were performed in 316 patients with LHD due to primary myocardial dysfunction or valvular disease. A total of 256 patients had PH-LHD, of whom 48% demonstrated DPGNEG . The V-wave amplitude inversely correlated with DPG (r = -0.45, P < 0.001) in patients with low pulmonary vascular resistance (PVR), but not in those with elevated PVR (P > 0.05). Patients with large V-waves had negative and lower DPG than those without augmented V-waves (P < 0.001) despite similar PVR (P >0.05). Positive, but normal DPG (0-6 mmHg) carried a worse 2-year prognosis for death and/or heart transplantation than DPGNEG (hazard ratio 2.97; P < 0.05). Our results advocate against DPGNEG constituting a measurement error. We propose that DPGNEG can partially be ascribed to large V-waves and carries a better prognosis than DPG within the normal positive range.

Back Support Shape with Pelvic Support Belt Affects Asymmetrical Seated Posture and Pressure Points During Reaching Tasks in Post-Stroke Patients

To investigate the effect of different back support shapes on asymmetrical seated posture and pressure points during a reaching task in post-stroke hemiplegic patients.

Numerical investigation of flow-induced rotary oscillation of circular cylinder with rigid splitter plate

Numerical results of fluid flow over a rotationally oscillating circular cylinder with splitter plate are presented here. Different from the previous examinations with freely rotatable assembly, the fluid and structure interactions are treated as a coupled dynamic system by fully considering the structural inertia, stiffness, and damping. The hydrodynamic characteristics are examined in terms of reduced velocity Ur at a relatively low Reynolds number Re = 100 for different plate lengths of L/D = 0.5, 1.0, and 1.5, where Ur = U/(Dfn), Re = UD/υ and fn = (κ/J)0.5/2π with U the free stream velocity, D the diameter of the circular cylinder, υ the fluid kinematic viscosity, fn the natural frequency, J the inertial moment, κ the torsional stiffness, and L the plate length. Contrast to the freely rotating cylinder/plate body, that is, in the limit of κ → 0 or Ur →∞, remarkable rotary oscillation is observed at relatively low reduced velocities. For the typical case with L/D = 1.0, the maximum amplitude may reach five times that at the highest reduced velocity of Ur = 15.0 considered in this work. At the critical reduced velocity Ur = 4.2, notable hydrodynamic jumps are identified for the rotation amplitude, response frequency, mean drag coefficient, lift amplitude, and vortex shedding frequency. Moreover, the phase angle between the fluid moment and rotary oscillation abruptly changes from 0 to π at Ur = 6.5. Due to the combined effect of fluid moment, rotation response, and phase difference, the natural frequency of the rotating body varies in flow, leading to a wide regime of lock-in/synchronization (Ur ≥4.2, for L/D = 1.0). The phenomenon of rotation bifurcation, i.e., the equilibrium position of the rotary oscillation deflects to a position which is not parallel to the free stream, is found to only occur at higher reduced velocities. The longer splitter plate has the lower critical reduced velocity. The occurrence of bifurcation is attributed to the anti-symmetry breaking of the wake flow evolution. The resultant asymmetric mean pressure distribution on the splitter plate gives rise to the net lift force and the deviated moment on the assembly, leading to the offset mean position of splitter plate. The global vortex shedding is identified to be the classic 2S mode for both cases with and without the bifurcation, although the second vortex formation and the shedding pattern in the near wake for the bifurcate case are different from the non-bifurcate case with lower reduced velocities.

Impact of Pressure and Temperature on Hydrogen Permeation in PEM Water Electrolyzers Operated at Asymmetric Pressure Conditions

Water electrolyzers are predominantly operated at elevated pressures. This is especially favorable in the context of the subsequent utilization of the produced hydrogen e.g. due to the more efficient, electrochemical and isothermal hydrogen compression or less afford for hydrogen drying. However, higher pressures lead to higher cross-permeation of the product gases in electrolysis cells. In the present contribution, hydrogen permeation across a fumea EF-40 membrane is systematically investigated for pressure differences between 5-35 bar and for four different temperatures between 22 °C and 60 °C. The measured permeation fluxes show a quadratic dependency on the pressure difference. A permeation model combining a diffusive and convective transport can describe the experimental data quantitatively. For the investigated membrane, the diffusive as well as the proposed convective permeability coefficient and their temperature dependencies are obtained. The diffusive permeability coefficient and its temperature dependency agrees very well with published data for Nafion membranes. The slightly lower value for the EF-40 can be explained by the lower water volume fraction. The obtained convective permeability coefficient indicates a high hydraulic permeability, especially in comparison to recently reported values for Nafion membranes. However, the reported values of the hydraulic permeability show high variations of about two orders of magnitude, with strong dependence on investigated materials, that show the importance of this parameter with regard to convective hydrogen permeation. The present work discusses two potential reasons for the high obtained hydraulic permeability. The first one is related to the membrane properties. In particular, the lower equivalent weight of the fumea EF-40 membrane could cause the higher hydraulic permeability. Second the electrolysis conditions, in particular the applied small current, might increase the hydraulic permeability due to wider membrane water channels and a change to a hydrophilic membrane surface. Figure: Parameterized equation in comparison to the experimental results. Figure 1

Impact of Pressure and Temperature on Hydrogen Permeation in PEM Water Electrolyzers Operated at Asymmetric Pressure Conditions

The present work investigates the hydrogen permeation through a polymer electrolyte membrane (PEM) of a fumea EF-40 catalyst coated membrane (CCM) during water electrolysis. The permeation rate is measured at different cell temperatures and different pressure gradients across the membrane. The determined permeation fluxes show a quadratic dependence on pressure difference. This can be described qualitatively very well with a permeation model that considers a diffusive and convective hydrogen transport through the membrane. The determined diffusive permeability coefficient Keff P,diff = 2.95E-14 mol/(m s Pa) at 60 °C and its temperature dependence agrees very well with comparable literature values. The proposed convective permeability coefficient Keff P,conv = 9.02E-21 mol/(m s Pa²) at 60 °C indicates a high hydraulic permeability for the investigated EF-40 in comparison with recently reported values for Nafion membranes.

Numerical Simulation of Fluidic Thrust-Vectoring

The paper focuses on a computational method for the investigation of Fluidic Thrust Vectoring (FTV). Thrust vectoring in symmetric nozzles is obtained by secondary flow injections that cause local flow separations, asymmetric pressure distributions and, therefore, the vectoring of the primary jet thrust. The methodology proposed here can be applied for studying numerically most of the strategies for fluidic thrust vectoring, as shock-vector control, sonic-plane skewing and the counterflow method. The computational technique is based on a well-assessed mathematical model. The flow governing equations are solved according to a finite volume discretization technique of the compressible RANS equations coupled with the Spalart-Allmaras turbulence model. Second order accuracy in space and time is achieved using an Essentially Non Oscillatory scheme. For validation purposes, the proposed numerical tool is used for the simulation of thrust vectoring based on FTV strategies as the shock vector control and the dual-throat nozzle concept, with a special attention to the latter case. Nozzle performances and thrust vector angles are computed for a wide range of nozzle pressure ratios and secondary flow injection rates. The numerical results obtained are compared with the experimental data available in the open literature.