Primary and secondary flow structures in ash-flow tuffs of the Gribbles Run paleovalley, central Colorado

1979 ◽  
pp. 137-154 ◽  
Author(s):  
Charles E. Chapin ◽  
Gary R. Lowell
Keyword(s):  
Secondary Flow ◽  
Flow Structures

Time-Resolved Measurements of the Unsteady Boundary Layer in an Annular Low-Pressure Turbine Configuration With Perturbed Inlet

2020 ◽  
Author(s):  
Martin Sinkwitz ◽  
Benjamin Winhart ◽  
David Engelmann ◽  
Francesca di Mare
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
Boundary Layers ◽  
Large Scale ◽  
Low Flow ◽  
Flow Structures ◽  
Stress System ◽  
Time Resolved ◽  
Blade Height ◽  
Profile Flow

Abstract In this study the unsteady behavior of the boundary layers developing on a LPT stator profile and their effect on secondary flow patterns in a 1.5-stage turbine configuration are investigated under the influence of periodic inflow perturbations. The experimental setup previously employed to analyze the unsteady secondary flow in the stator wake has been enhanced by hotfilm sensor arrays placed on the stator profiles at different blade height positions to provide time-resolved data from within the passage. The turbine inflow is perturbed by periodically passing circular bars and a modified T106-profile has been considered for the blading. The modified profile, labeled as T106RUB, was developed for matching the transition and separation characteristics of the original T106 profile at low flow speeds, thus facilitating measurements to be taken in a large-scale test rig with its improved accessibility. The transition phenomena occurring in the profile boundary layers are investigated under both unperturbed and periodically perturbed inflow by means of spectral analysis, the semi-quantitative characterization of the wall-stress system and an evaluation of the statistic quantities. In particular, the periodic changes of the suction side boundary layer flow region towards the trailing edge are studied in detail. Furthermore, time-resolved hot-film measurements at different blade height positions facilitate a detailed comparison of the quasi two-dimensional mid-span profile flow and the near end wall profile flow which is subject to influence of secondary flow structures. These information are employed to assess to which extent the additional turbulence originating from the wakes affects the blade boundary layers and thus the secondary flow structures. Furthermore, the role of the perturbation frequency on the coupled system of boundary layers and secondary flow structures is evaluated.

Unsteady RANS Simulation of Turbulent Flow and Heat Transfer in Ribbed Coolant Passages of Different Aspect Ratios

2004 ◽  
Author(s):  
A. K. Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Rotation Number ◽  
Large Scale ◽  
Density Ratio ◽  
Navier Stokes ◽  
Flow Structures ◽  
Flow And Heat Transfer ◽  
Aspect Ratios ◽  
Unsteady Rans

The flow and heat transfer in ribbed coolant passages of aspect ratios (AR) of 1:1, 4:1, and 1:4 are numerically studied through the solution of the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations. The ribs are oriented normal to the flow and arranged in a staggered configuration on the leading and trailing surfaces. The URANS procedure can resolve large-scale bulk unsteadiness, and utilizes a two equation k-ε model for the turbulent stresses. Both Coriolis and centrifugal buoyancy effects are included in the simulations. The computations are carried out for a fixed Reynolds number of 25000 and density ratio of 0.13 while the Rotation number has been varied between 0.12–0.50. The average duct heat transfer is the highest for the 4:1 AR case. For this case, the secondary flow structures consist of multiple roll cells that direct flow both to the trailing and leading surfaces. The 1:4 AR duct shows flow reversal along the leading surface at high rotation numbers with multiple rolls in the secondary flow structures near the leading wall. For this AR, the potential for conduction-limited heat transfer along the leading surface is identified. At high rotation number, both the 1:1 and 4:1 AR cases exhibit loss of axial periodicity over one inter-rib module. The friction factor reveals an increase with the rotation number for all aspect ratio ducts, and shows a sudden jump in its value at a critical rotation number because of either loss of spatial periodicity or the onset of backflow.

Effects of an Upstream Cavity on the Secondary Flow in a Transonic Turbine Cascade

2010 ◽  
Author(s):  
H. M. Abo El Ella ◽  
S. A. Sjolander ◽  
T. J. Praisner
Keyword(s):  
Mach Number ◽  
Secondary Flow ◽  
Ultra Violet ◽  
Leading Edge ◽  
Reactive Dye ◽  
Surface Flow ◽  
Flow Structures ◽  
Pressure Probe ◽  
Turbine Cascade ◽  
Blow Down

This paper examines experimentally the effects of an upstream cavity on the flow structures and secondary losses in a transonic linear turbine cascade. The cavity approximates the endwall geometry resulting from the platform overlap at the interface between stationary and rotating turbine blade rows. Previous investigations of the effects of upstream cavity geometries have been conducted mainly at low-speed conditions. The present work aims to extend such research into the transonic regime with a more engine representative upstream platform geometry. The investigations were carried out in a blow-down type wind tunnel. The cavity is located at 30% of axial-chord from the leading edge, extends 17% of axial-chord in depth, and is followed by a smooth ramp to return the endwall to its nominal height. Two cascades are examined for the same blade geometry: the baseline cascade with a flat endwall and the cascade with the cavity endwall. Measurements were made at the design incidence and the outlet design Mach number of 0.80. At this condition, the Reynolds number based on outlet velocity is about 600,000. Off-design outlet Mach numbers of 0.69, and 0.89 were also investigated. Flowfield measurements were carried out at 40% axial-chord downstream of the trailing edge, using a seven-hole pressure probe, to quantify losses and identify the flow structures. Additionally, surface flow visualization using an ultra-violet reactive dye was employed at the design Mach number, on the endwall and blade surfaces, to help in the interpretation of the flow physics. The experimental results also include blade-loading distributions, and the probe measurements were processed to obtain total-pressure loss coefficients, and stream-wise vorticity distributions. It was found that the presence of the upstream cavity noticeably altered the structure and the strength of the secondary flow. Some effect on the secondary losses was also evident, with the cavity having a larger effect at the higher Mach number.

Experimental and Numerical Investigation of Secondary Flow Structures in an Annular Low Pressure Turbine Cascade Under Periodic Wake Impact—Part 2: Numerical Results

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Benjamin Winhart ◽  
Martin Sinkwitz ◽  
Andreas Schramm ◽  
David Engelmann ◽  
Francesca di Mare ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Direct Interaction ◽  
Numerical Data ◽  
Horseshoe Vortex ◽  
Low Pressure ◽  
Navier Stokes ◽  
Flow Structures ◽  
Pressure Loss Coefficient ◽  
Low Pressure Turbine ◽  
Numerical Predictions

In this work, we present the results of the numerical investigations of periodic wake–secondary flow interaction carried out on a low pressure turbine (LPT) equipped with modified T106-profile blades. The numerical predictions obtained by means of unsteady Reynolds-averaged Navier–Stokes (URANS) simulations using a k-ω-model have been compared with measurements conducted in the same configuration and showed a good agreement. Based on the verified numerical data, the Q-criterion has been employed to characterize the secondary flow structures and accurately identify their origin. An analysis of the fundamental wake kinematics and the unsteady vortex migration revealed dominant interaction mechanisms such as the circumferential fluctuation of the pressure side horseshoe vortex (HSV) and its direct interaction with the passage vortex (PV) and the concentrated shed vortex (CSV). Finally, a correlation with the total pressure loss coefficient is provided and a link to the incoming wake structures is given.

scholarly journals Experimental and Computational Study of the Unsteady Flow in a 1.5 Stage Axial Turbine With Emphasis on the Secondary Flow in the Second Stator

1998 ◽  
Author(s):  
Ralf E. Walraevens ◽  
Heinz E. Gallus ◽  
Alexander R. Jung ◽  
Jürgen F. Mayer ◽  
Heinz Stetter
Keyword(s):  
Unsteady Flow ◽  
Secondary Flow ◽  
Computational Study ◽  
Three Dimensional ◽  
Cross Flow ◽  
Axial Flow ◽  
Time Dependent ◽  
Flow Structures ◽  
Mean Flow ◽  
Dependent Flow

A study of the unsteady flow in an axial flow turbine stage with a second stator blade row is presented. The low aspect ratio blades give way to a highly three-dimensional flow which is dominated by secondary flow structures. Detailed steady and unsteady measurements throughout the machine and unsteady flow simulations which include all blade rows have been carried out. The presented results focus on the second stator flow. Secondary flow structures and their origins are identified and tracked on their way through the passage. The results of the time-dependent secondary velocity vectors as well as flow angles and Mach number distributions as perturbation from the time-mean flow field are shown in cross-flow sections and azimuthal cuts throughout the domain of the second stator. At each location the experimental and numerical results are compared and discussed. A good overall agreement in the time-dependent flow behaviour as well as in the secondary flow structures is stated.

The Effect of Profile Contouring on Secondary Flow Structures in Low Pressure Turbines

2016 ◽  
Author(s):  
Philip S. Bear ◽  
Mitch Wolff ◽  
Christopher R. Marks ◽  
Rolf Sondergaard
Keyword(s):  
Secondary Flow ◽  
Low Pressure ◽  
Flow Structures

New Facility Setup for the Investigation of Cooling Flow, Viscous and Rotational Effects on the Interstage Seal Flow Behavior of a Gas Turbine

2018 ◽  
Author(s):  
R. Guida ◽  
D. Lengani ◽  
D. Simoni ◽  
M. Ubaldi ◽  
P. Zunino
Keyword(s):  
Secondary Flow ◽  
Flow Rate ◽  
Discharge Coefficient ◽  
Flow Path ◽  
Main Flow ◽  
Coolant Flow ◽  
Flow Structures ◽  
Cooling Flow ◽  
Wall Flow ◽  
Near Wall

A new rig has been designed and commissioned at the University of Genova to study the flow field within a turbine interstage cavity and its interaction with the main flow path. The rig is a large scale one-and-half stages, rotating test facility, opportunely designed to reproduce the main features characterizing the cavity flows developing in real low pressure modules of turbogas engines. The effects due to swirl factor and the coolant injected into the cavity to prevent the thermomechanical failure of the disks have been investigated. The rig allows the evaluation of the leakage mass flow rate and the measurement of the seal discharge coefficient in the different operating conditions, as well as the characterization of viscous, rotational and coolant related effects on the main flow path, especially in terms of secondary flow structures and vane row efficiency. Pressure signals acquired into the cavity provide a direct measure of the pressurization level of the fore and rear cavities, as well as the analysis of the effects induced by rotation and coolant flow on the pressure drop provoked by the teeth. Results clearly show that once the cooling flow rate reaches a datum threshold level an iso-pressure condition (with respect to the main flow at the vane leading edge) is established into the fore part of the cavity, and the gas ingestion from the main annulus is avoided. This “purged” condition significantly modifies the near wall flow developing across the vane. The boundary layer entering the vane row is not sucked into the cavity, and simultaneously at the vane exit plane there is poor interaction between the cavity flow and the near wall flow leaving the vane. Total pressure measurements upstream and downstream of the vane clearly highlight the modification of the secondary flow structures for the different conditions tested. Overall, results reported into the paper demonstrate the capability of the new rig to provide a direct estimation of the discharge coefficient of a realistic turbine cavity system for different coolant flow rates and swirl factors, as well as to understand the effects on the flow path near wall behavior due to cavity-main flows interaction, that should be properly accounted for during the design phases, and should be properly reproduced during cascade testing.

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