A Time-Lag Approach for Prediction of Trailing Edge Separation in Unsteady Flow

2014 ◽  
Author(s):  
Shreyas Narsipur ◽  
Ashok Gopalarathnam ◽  
Jack R. Edwards
Keyword(s):  
Unsteady Flow ◽  
Time Lag ◽  
Trailing Edge ◽  
Edge Separation

scholarly journals Low-Order Model for Prediction of Trailing-Edge Separation in Unsteady Flow

AIAA Journal ◽  
2019 ◽  
Vol 57 (1) ◽  
pp. 191-207 ◽  
Author(s):  
Shreyas Narsipur ◽  
Ashok Gopalarathnam ◽  
Jack R. Edwards
Keyword(s):  
Unsteady Flow ◽  
Order Model ◽  
Trailing Edge ◽  
Edge Separation ◽  
Low Order

Three-Dimensional and Rotational Aerodynamics on the NREL Phase VI Wind Turbine Blade

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Alvaro Gonzalez ◽  
Xabier Munduate
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Three Dimensional ◽  
Separated Flow ◽  
Leading Edge ◽  
Wind Turbine Blade ◽  
Trailing Edge ◽  
Rotating Blade ◽  
Nrel Phase Vi ◽  
Edge Separation

This work undertakes an aerodynamic analysis over the parked and the rotating NREL Phase VI wind turbine blade. The experimental sequences from NASA Ames wind tunnel selected for this study respond to the parked blade and the rotating configuration, both for the upwind, two-bladed wind turbine operating at nonyawed conditions. The objective is to bring some light into the nature of the flow field and especially the type of stall behavior observed when 2D aerofoil steady measurements are compared to the parked blade and the latter to the rotating one. From averaged pressure coefficients together with their standard deviation values, trailing and leading edge separated flow regions have been found, with the limitations of the repeatability of the flow encountered on the blade. Results for the parked blade show the progressive delay from tip to root of the trailing edge separation process, with respect to the 2D profile, and also reveal a local region of leading edge separated flow or bubble at the inner, 30% and 47% of the blade. For the rotating blade, results at inboard 30% and 47% stations show a dramatic suppression of the trailing edge separation, and the development of a leading edge separation structure connected with the extra lift.

Computational Study of the Risø-B1-18 Airfoil with a Hinged Flap Providing Variable Trailing Edge Geometry

2005 ◽  
Vol 29 (2) ◽  
pp. 89-113 ◽  
Author(s):  
Niels Troldborg
Keyword(s):  
Reynolds Number ◽  
Unsteady Flow ◽  
Computational Study ◽  
Turbine Blades ◽  
Aerodynamic Characteristics ◽  
Flow Conditions ◽  
Wind Turbine Blades ◽  
Trailing Edge ◽  
Edge Geometry ◽  
Fully Developed Turbulent Flow

A comprehensive computational study, in both steady and unsteady flow conditions, has been carried out to investigate the aerodynamic characteristics of the Risø-B1-18 airfoil equipped with variable trailing edge geometry as produced by a hinged flap. The function of such flaps should be to decrease fatigue-inducing oscillations on the blades. The computations were conducted using a 2D incompressible RANS solver with a k-w turbulence model under the assumption of a fully developed turbulent flow. The investigations were conducted at a Reynolds number of Re = 1.6 · 106. Calculations conducted on the baseline airfoil showed excellent agreement with measurements on the same airfoil with the same specified conditions. Furthermore, a more widespread comparison with an advanced potential theory code is presented. The influence of various key parameters, such as flap shape, flap size and oscillating frequencies, was investigated so that an optimum design can be suggested for application with wind turbine blades. It is concluded that a moderately curved flap with flap chord to airfoil curve ratio between 0.05 and 0.10 would be an optimum choice.

Combination of DES and DDES with a Correlation Based Transition Model

2013 ◽  
Vol 444-445 ◽  
pp. 374-379 ◽  
Author(s):  
Lei Qiao ◽  
Jun Qiang Bai ◽  
Jun Hua ◽  
Chen Wang
Keyword(s):  
Present Article ◽  
Test Case ◽  
Transition Model ◽  
Detached Eddy Simulation ◽  
Combined Model ◽  
Trailing Edge ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Stall Angle ◽  
Edge Separation

The present article describes the combination of the correlation based transition model of Menter et al. with the Detached Eddy Simulation (DES) and Delayed Detached Eddy Simulation (DDES) methodology. The interaction between transition model and DES or DDES method was investigated by T3A test case. The grid sensitivity of the combined methodology is discussed and the resolution is given. Then, the simulation of flow over foil of medium thick at stall angle was performed. The combined methodology produce results that have better agreement with experiment comparing to RANS transition model or fully turbulent DES/DDES alone. And the DDES based combined model shows a better agreement with experiment in the simulation of trailing edge separation comparing to DES based combined model.

Unsteady Turbine Rim Sealing and Vane Trailing Edge Flow Effects

2021 ◽  
Author(s):  
Iván Monge-Concepción ◽  
Shawn Siroka ◽  
Reid A. Berdanier ◽  
Michael D. Barringer ◽  
Karen A. Thole ◽  
...  
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Rotational Speed ◽  
Large Scale ◽  
Trailing Edge ◽  
Time Resolved ◽  
Flow Rates ◽  
Large Scale Structures ◽  
Purge Flow ◽  
Scale Structures

Abstract Hot gas ingestion into the turbine rim seal cavity is an important concern for engine designers. To prevent ingestion, rim seals use high pressure purge flow but excessive use of the purge flow decreases engine thermal efficiency. A single stage test turbine operating at engine-relevant conditions with real engine hardware was used to study time-resolved pressures in the rim seal cavity across a range of sealing purge flow rates. Vane trailing edge (VTE) flow, shown previously to be ingested into the rim seal cavity, was also included to understand its effect on the unsteady flow field. Measurements from high-frequency response pressure sensors in the rim seal and vane platform were used to determine rotational speed and quantity of large-scale structures (cells). In a parallel effort, a computational model using Unsteady Reynolds-averaged Navier-Stokes (URANS) was applied to determine swirl ratio in the rim seal cavity and time-resolved rim sealing effectiveness. The experimental results confirm that at low purge flow rates, the VTE flow influences the unsteady flow field by decreasing pressure unsteadiness in the rim seal cavity. Results show an increase in purge flow increases the number of unsteady large-scale structures in the rim seal and decreases their rotational speed. However, VTE flow was shown to not significantly change the cell speed and count in the rim seal. Simulations point to the importance of the large-scale cell structures in influencing rim sealing unsteadiness, which is not captured in current rim sealing predictive models.

Control of trailing-edge separation by tangential blowing inside the bubble

2004 ◽  
Vol 108 (1086) ◽  
pp. 419-425 ◽  
Author(s):  
P. R. Viswanath ◽  
K. T. Madhavan
Keyword(s):  
Separation Bubble ◽  
Effective Means ◽  
Separated Flow ◽  
Wake Flow ◽  
Turbulent Shear ◽  
Trailing Edge ◽  
Mean Velocity ◽  
Turbulent Shear Stress ◽  
Edge Separation ◽  
Tangential Blowing

Abstract Experiments have been performed investigating the effectiveness of steady tangential blowing, with the blowing slot located downstream of separation (but inside the separation bubble) to control a trailing-edge separated flow at low speeds. Trailing-edge separation was induced on a two-dimensional aerofoil-like body and the shear layer closure occurred in the near-wake. Measurements made consisted of model surface pressures and mean velocity, turbulent shear stress and kinetic energy profiles in the separated zone using a two-component LDV system. It is explicitly demonstrated that the novel concept of tangential blowing inside the bubble can be an effective means of control for trailing-edge separated flows as well. Blowing mass and momentum requirements for the suppression of wall and wake flow reversals have been estimated.

scholarly journals Unsteady Flow Field Due to Nozzle Wake Interaction With the Rotor in an Axial Flow Turbine: Part II—Rotor Exit Flow Field

1997 ◽  
Vol 119 (2) ◽  
pp. 214-224 ◽  
Author(s):  
M. A. Zaccaria ◽  
B. Lakshminarayana
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Velocity Component ◽  
Axial Flow ◽  
Turbine Rotor ◽  
Edge Region ◽  
Trailing Edge ◽  
Rotor Wake ◽  
Cross Correlations ◽  
Far Wake

The two-dimensional steady and unsteady flow field at midspan in a turbine rotor has been investigated experimentally using an LDV with an emphasis on the interaction of the nozzle wake with the rotor flow field. The velocity measurements are decomposed into a time-averaged velocity, a periodic velocity component, and an unresolved velocity component. The results in the rotor passage were presented in Part I. The flow field downstream of the rotor is presented in this paper. The rotor wake profiles and their decay characteristics were analyzed. Correlations are presented that match the decay of the various wake properties. The rotor wake velocity defect decays rapidly in the trailing edge region, becoming less rapid in the near and far wake regions. The rotor wake semi-wake width increases rapidly in the trailing edge region and then grows more gradually in the near and far wake regions. The decay of the maximum unresolved unsteadiness and maximum unresolved velocity cross correlations is very rapid in the trailing edge region and this trend slows in the far wake region. In the trailing edge region, the maximum periodic velocity correlations are much larger than the maximum unresolved velocity correlations. But the periodic velocity correlations decay much faster than the unresolved velocity correlations. The interactions of the nozzle and rotor wakes are also studied. While the interaction of the nozzle wake with the rotor wake does not influence the decay rate of the various wake properties, it does change the magnitude of the properties. These and other results are presented in this paper.

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