Numerical Modeling of a Wave Turbine and Estimation of Shaft Work

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Ravichandra R. Jagannath ◽  
Sally P. M. Bane ◽  
M. Razi Nalim
Keyword(s):  
Angular Momentum ◽  
Dynamic Pressure ◽  
Work Output ◽  
Reference Case ◽  
Efficient Energy Transfer ◽  
Curvature Effects ◽  
Axial Channel ◽  
Curved Channels ◽  
Wave Rotors ◽  
Pressure Exchange

Wave rotors are periodic-flow devices that provide dynamic pressure exchange and efficient energy transfer through internal pressure waves generated due to fast opening and closing of ports. Wave turbines are wave rotors with curved channels that can produce shaft work through change of angular momentum from inlet to exit. In the present work, conservation equations with averaging in the transverse directions are derived for wave turbines, and quasi-one-dimensional model for axial-channel non-steady flow is extended to account for blade curvature effects. The importance of inlet incidence is explained and the duct angle is optimized to minimize incidence loss for a particular boundary condition. Two different techniques are presented for estimating the work transfer between the gas and rotor due to flow turning, based on conservation of angular momentum and of energy. The use of two different methods to estimate the shaft work provides confidence in reporting of work output and confirms internal consistency of the model while it awaits experimental data for validation. The extended wave turbine model is used to simulate the flow in a three-port wave rotor. The work output is calculated for blades with varying curvature, including the straight axial channel as a reference case. The dimensional shaft work is reported for the idealized situation where all loss-generating mechanisms except flow incidence are absent, thus excluding leakage, heat transfer, friction, port opening time, and windage losses. The model developed in the current work can be used to determine the optimal wave turbine designs for experimental investment.

Flows in a rotating spherical shell: the equatorial case

1994 ◽  
Vol 276 ◽  
pp. 233-260 ◽  
Author(s):  
A. Colin de Verdière ◽  
R. Schopp
Keyword(s):  
Angular Momentum ◽  
Rotation Axis ◽  
Dynamic Pressure ◽  
Vertical Component ◽  
Low Frequency ◽  
Zonal Flow ◽  
Horizontal Component ◽  
Meridional Plane ◽  
Earth’S Rotation ◽  
Earth's Rotation

It is well known that the widely used powerful geostrophic equations that single out the vertical component of the Earth's rotation cease to be valid near the equator. Through a vorticity and an angular momentum analysis on the sphere, we show that if the flow varies on a horizontal scale L smaller than (Ha)1/2 (where H is a vertical scale of motion and a the Earth's radius), then equatorial dynamics must include the effect of the horizontal component of the Earth's rotation. In equatorial regions, where the horizontal plane aligns with the Earth's rotation axis, latitudinal variations of planetary angular momentum over such scales become small and approach the magnitude of its radial variations proscribing, therefore, vertical displacements to be freed from rotational constraints. When the zonal flow is strong compared to the meridional one, we show that the zonal component of the vorticity equation becomes (2Ω.Δ)u1 = g/ρ0)(∂ρ/a∂θ). This equation, where θ is latitude, expresses a balance between the buoyancy torque and the twisting of the full Earth's vorticity by the zonal flow u1. This generalization of the mid-latitude thermal wind relation to the equatorial case shows that u1 may be obtained up to a constant by integrating the ‘observed’ density field along the Earth's rotation axis and not along gravity as in common mid-latitude practice. The simplicity of this result valid in the finite-amplitude regime is not shared however by the other velocity components.Vorticity and momentum equations appropriate to low frequency and predominantly zonal flows are given on the equatorial β-plane. These equatorial results and the mid-latitude geostrophic approximation are shown to stem from an exact generalized relation that relates the variation of dynamic pressure along absolute vortex lines to the buoyancy field. The usual hydrostatic equation follows when the aspect ratio δ = H/L is such that tan θ/δ is much larger than one. Within a boundary-layer region of width (Ha)1/2 and centred at the equator, the analysis shows that the usually neglected Coriolis terms associated with the horizontal component of the Earth's rotation must be kept.Finally, some solutions of zonally homogeneous steady equatorial inertial jets are presented in which the Earth's vorticity is easily turned upside down by the shear flow and the correct angular momentum ‘Ωr2cos2(θ)+u1rCos(θ)’ contour lines close in the vertical–meridional plane.

Surface-layer similarity in turbulent circular Couette flow

1984 ◽  
Vol 144 ◽  
pp. 123-131 ◽  
Author(s):  
Martin Claussen
Keyword(s):  
Surface Layer ◽  
Angular Momentum ◽  
Free Convection ◽  
Couette Flow ◽  
Similarity Theory ◽  
Outer Region ◽  
Cylinder Wall ◽  
Curvature Effects ◽  
Circular Couette Flow ◽  
Very High

Smith & Townsend's (1982) experimental data on circular Couette flow are re-examined in the framework of surface-layer similarity theory. Surface-layer similarity of horizontally stratified shear flow is shown to have its counterpart in a narrow-gap Couette flow between concentric cylinders. Smith & Townsend's data of mean angular momentum and mean-velocity profiles in a region near a cylinder lend support to the applicability of Monin–Obukhov similarity to circular Couette flow. Only for flows of very high Reynolds numbers is a region of logarithmic variation of mean profiles found close to the cylinder wall. Because of curvature effects on the flow, the mean profiles deviate from the logarithmic profile as distance from the cylinder wall increases. For flows of sufficiently low Reynolds number, but still very high Taylor number, no logarithmic profile seems to exist; instead, profiles in the viscous region and in the outer region are connected to each other by a ‘free-convection (rotation)’ profile. From Smith & Townsend's data the velocity field is not observed to follow the prediction of ‘free-convection’ similarity; however, the ‘free-convection’ profile is found in the distribution of mean angular momentum.

scholarly journals Performance assessment of solar chimney power plants with the impacts of divergent and convergent chimney geometry

2021 ◽  
Author(s):  
Erdem Cuce ◽  
Abhishek Saxena ◽  
Pinar Mert Cuce ◽  
Harun Sen ◽  
Shaopeng Guo ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Power Plants ◽  
Dynamic Pressure ◽  
Electrical Power ◽  
Independent Solution ◽  
System Efficiency ◽  
Solar Chimney ◽  
Reference Case

Abstract Influence of area ratio (AR) on main performance parameters of solar chimney power plants (SCPPs) is investigated through a justified 3D axisymmetric CFD model. Geometric characteristics of Manzanares pilot plant (MPP) are taken into consideration for the numerical model. AR is varied from 0.5 to 10 to cover both concave and convex (convergent and divergent) solar chimney designs. Following the accuracy verification of the CFD results and proving mesh-independent solution, main performance oriented parameters are assessed as a function of AR such as velocity, temperature and pressure distribution within MPP, temperature rise of air in collector, mass flow rate of air around the turbine area, dynamic pressure difference across the turbine, minimum static pressure in the entire plant, power output and system efficiency. The results reveal that AR plays a vital role in performance figures of MPP. Mass flow rate of air ($\dot{m}$) is found to be 1122.1 kg/s for the reference geometry (AR = 1), whereas it is 1629.1 kg/s for the optimum AR value of 4. System efficiency (η) is determined to be 0.29% for the reference case; however, it is enhanced to 0.83% for the AR of 4.1. MPP can generate 54.3 kW electrical power in its current design while it is possible to improve this figure to 168.5 kW with the optimal AR value.

scholarly journals Leakage Assessment of Pressure-Exchange Wave Rotors

2008 ◽  
Vol 24 (4) ◽  
pp. 732-740 ◽  
Author(s):  
P. Akbari ◽  
M. R. Nalim ◽  
E. S. Donovan ◽  
P. H. Snyder
Keyword(s):  
Wave Rotors ◽  
Pressure Exchange ◽  
Leakage Assessment

scholarly journals Dynamic aerosol and dynamic air-water interface curvature effects on a 2-Gbit/s free-space optical link using orbital-angular-momentum multiplexing

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Haoqian Song ◽  
Runzhou Zhang ◽  
Nanzhe Hu ◽  
Huibin Zhou ◽  
Xinzhou Su ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Power Loss ◽  
Water Interface ◽  
Coupling Ratio ◽  
Power Coupling ◽  
Curvature Effects ◽  
Wavefront Distortion ◽  
Modal Power ◽  
Beam Wandering ◽  
Air Water Interface

Abstract When an orbital-angular-momentum (OAM) beam propagates through the dynamic air–water interface, the aerosol above the water and the water surface curvature could induce various degradations (e.g., wavefront distortion, beam wandering, scattering, and absorption). Such time-varying degradations could affect the received intensity and phase profiles of the OAM beams, resulting in dynamic modal power loss and modal power coupling. We experimentally investigate the degradation for a single OAM beam under dynamic aerosol, dynamic curvature, and their comprehensive effects. Our results show the following: (i) with the increase of the aerosol strength (characterized by the attenuation coefficient) from ∼0 to ∼0.7–1.3 dB/cm over ∼7 cm, the power coupling ratio from OAM −1 to +2 increases by 4 dB, which might be due to the amplitude and phase distortion caused by spatially dependent scattering and absorption. (ii) With the increase of the curvature strength (characterized by the variance of curvature slope over time) from ∼0 to ∼2 × 10−5 rad2, the power coupling ratio from OAM −1 to +2 increases by 11 dB. This could be caused by both the wavefront distortion and the beam wandering. (iii) Under the comprehensive effect of aerosol (∼0.1–0.6 dB/cm) and curvature (∼6 × 10−7 rad2), there is an up to 2 dB higher modal power loss as compared with the single-effect cases. (iv) The received power on OAM −1 fluctuates in a range of ∼6 dB within a 220 ms measurement time under aerosol (∼0.1–0.6 dB/cm) and curvature (∼6 × 10−7 rad2) effects due to the dynamic degradations. We also demonstrate an OAM −1 and +2 multiplexed 2-Gbit/s on–off-keying link under dynamic aerosol and curvature effects. The results show a power penalty of ∼3 dB for the bit-error-rate at the 7% forward-error-correction limit under the comprehensive effect of aerosol (∼0.1–0.6 dB/cm) and curvature (∼6 × 10−7 rad2), compared with the no-effect case.

The Effects of Direction and Velocity of Movement, and Intra-Articular Fluid Volume on Intra-Articular Pressue

1988 ◽  
Vol 01 (03/04) ◽  
pp. 113-121 ◽  
Author(s):  
S. F. Straface ◽  
P. J. Newbold ◽  
S. Nade
Keyword(s):  
Dynamic Pressure ◽  
Volume Of Fluid ◽  
Joint Capsule ◽  
Fluid Volume ◽  
Structural Configuration

levels. In joints with simulated acute effusion the effect of position on IAP was dependent upon the volume of fluid in the joint. The results indicate that dynamic pressure levels in the moving knee are related to the movements of the joint. The characteristic and reproducible patterns of pressure may reflect changes in the structural configuration of the joint capsule and surrounding tissues during movement, and are influenced by the amount of fluid in the joint.

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