Analytical actuator disc solution for unsteady load

2016 ◽  
Author(s):  
Wei Yu ◽  
Carlos Simao Ferreira ◽  
Gijs van Kuik
Keyword(s):  
Actuator Disc

Fractal-like actuator disc theory for optimal energy extraction

2021 ◽  
Vol 927 ◽  
Author(s):  
D. Dehtyriov ◽  
A.M. Schnabl ◽  
C.R. Vogel ◽  
S. Draper ◽  
T.A.A. Adcock ◽  
...  
Keyword(s):  
Extraction Process ◽  
Power Coefficient ◽  
Finite Width ◽  
Energy Extraction ◽  
Optimal Arrangement ◽  
Planar System ◽  
Power Extraction ◽  
Multi Scale ◽  
Actuator Disc ◽  
Inner Scale

The limit of power extraction by a device which makes use of constructive interference, i.e. local blockage, is investigated theoretically. The device is modelled using actuator disc theory in which we allow the device to be split into arrays and these then into sub-arrays an arbitrary number of times so as to construct an $n$ -level multi-scale device in which the original device undergoes $n-1$ sub-divisions. The alternative physical interpretation of the problem is a planar system of arrayed turbines in which groups of turbines are homogeneously arrayed at the smallest $n\mathrm {th}$ scale, and then these groups are homogeneously spaced relative to each other at the next smallest $n-1\mathrm {th}$ scale, with this pattern repeating at all subsequent larger scales. The scale-separation idea of Nishino & Willden (J. Fluid. Mech., vol. 708, 2012b, pp. 596–606) is employed, which assumes mixing within a sub-array occurs faster than mixing of the by-pass flow around that sub-array, so that in the $n$ -scale device mixing occurs from the inner scale to the outermost scale in that order. We investigate the behaviour of an arbitrary level multi-scale device, and determine the arrangement of actuator discs ( $n\mathrm {th}$ level devices) which maximises the power coefficient (ratio of power extracted to undisturbed kinetic energy flux through the net disc frontal area). We find that this optimal arrangement is close to fractal, and fractal arrangements give similar results. With the device placed in an infinitely wide channel, i.e. zero global blockage, we find that the optimum power coefficient tends to unity as the number of device scales tends to infinity, a 27/16 increase over the Lanchester–Betz limit of $0.593$ . For devices in finite width channels, i.e. non-zero global blockage, similar observations can be made with further uplift in the maximum power coefficient. We discuss the fluid mechanics of this energy extraction process and examine the scale distribution of thrust and wake velocity coefficients. Numerical demonstration of performance uplift due to multi-scale dynamics is also provided. We demonstrate that bypass flow remixing and ensuing energy losses increase the device power coefficient above the limits for single devices, so that although the power coefficient can be made to increase, this is at the expense of the overall efficiency of energy extraction which decreases as wake-scale remixing losses necessarily rise. For multi-scale devices in finite overall blockage two effects act to increase extractable power; an overall streamwise pressure gradient associated with finite blockage, and wake pressure recoveries associated with bypass-scale remixing.

Wake Comparison of Open and Ducted Wind Turbines Using Actuator Disc Simulations

2021 ◽  
Author(s):  
Nojan Bagheri Sadeghi ◽  
Brian Helenbrook ◽  
Kenneth Visser
Keyword(s):  
Wind Turbines ◽  
Actuator Disc

scholarly journals Comparison of actuator disc and Joukowsky rotor flows, to explore the need for a tip correction

2015 ◽  
Vol 625 ◽  
pp. 012013 ◽  
Author(s):  
Gijs van Kuik ◽  
Wei Yu ◽  
Sasan Sarmast ◽  
Stefan Ivanell
Keyword(s):  
Actuator Disc

scholarly journals Kinetic energy entrainment in wind turbine and actuator disc wakes: an experimental analysis

2014 ◽  
Vol 524 ◽  
pp. 012163 ◽  
Author(s):  
L E M Lignarolo ◽  
D Ragni ◽  
C J Simão Ferreira ◽  
G J W van Bussel
Keyword(s):  
Kinetic Energy ◽  
Wind Turbine ◽  
Experimental Analysis ◽  
Actuator Disc

Trapped acoustic modes in aeroengine intakes with swirling flow

2000 ◽  
Vol 419 ◽  
pp. 151-175 ◽  
Author(s):  
A. J. COOPER ◽  
N. PEAKE
Keyword(s):  
Swirling Flow ◽  
Aircraft Engine ◽  
Acoustic Resonance ◽  
Axial Fan ◽  
System Parameters ◽  
Acoustic Modes ◽  
Resonant States ◽  
Blade Row ◽  
Actuator Disc ◽  
Axial Variation

A theoretical model of an aeroengine intake–fan system is developed in order to show the existence of acoustic resonance in the intake. In general this phenomenon can be linked to instabilities in aircraft engine inlets.The model incorporates a slowly varying duct intake and accounts for the swirling flow downstream of the fan. The slow axial variation in cross-section gives rise to turning points where upstream-propagating acoustic modes are totally reflected into downstream-propagating modes. The effect of the swirling flow downstream can be to cut off a mode which is cut on upstream of the fan. It is shown that these two aspects of the flow, coupled with the effects of the fan (represented by an actuator disc), can lead to acoustic modes becoming trapped in the intake, thus giving rise to pure acoustic resonance.A whole range of system parameters, such as axial, fan and swirl Mach numbers, which satisfy the conditions for resonance are identified. The effects of a stationary blade row behind the fan are also considered leading to a second family of resonant states. In addition we find resonance due to reflection of acoustic modes at the open (inlet) end of the duct.

A Review of Inlet-Fan Coupling Methodologies

2017 ◽  
Author(s):  
Benjamin Godard ◽  
Edouard De Jaeghere ◽  
Nabil Ben Nasr ◽  
Julien Marty ◽  
Raphael Barrier ◽  
...  
Keyword(s):  
Experimental Data ◽  
Industrial Design ◽  
Body Force ◽  
The Body ◽  
Source Terms ◽  
Force Modeling ◽  
Actuator Disc ◽  
Flow Deviation ◽  
New Challenges ◽  
Bypass Ratio

With the rise of ultra high bypass ratio turbofan and shorter and slimmer inlet geometries compared to classical architectures, designers face new challenges as nacelle and fan design cannot anymore be addressed independently. This paper reviews CFD methods developed to simulate inlet-fan interactions and suitable for industrial design cycles. In addition to the reference isolated fan and nacelle models, the methodologies evaluated in this study consist of two fan modeling approaches, an actuator disc and body-force source terms. The configuration is a modern turbofan with a high bypass ratio under cross-wind. Results are compared to experimental data. As to be predicted, the body-force modeling approach enables early inlet reattachment. In addition, it provides a representative flow deviation across the fan zone which enables performance and stability assessments.

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