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Measurement of wind effects on a 300-M concrete chimney — reference paramters
Abstract
Indirect methods based on the measured pressure distribution around a chimney frequently represent the only means of determining the primary reference parameter in a chimney experiment, the free-stream dynamic pressure. But because pressures are generally measured relative to an unknown reference pressure, these methods rely on assumptions which may lead to unpredictable results. In this particular experiment assumptions were avoided by using a specially developed barometric pressure probe, suspended from a cable strung between two chimneys. Measurements are presented to show that acceptable results can be obtained by assuming the zero-crossing angle of the pressure distribution.
... In (Sanada et al., 1992), a full-scale pressure measurement on 200 m concrete chimney with rough surface measured the mean drag coefficient as 0.62 in Re = 3 − 4⋅10 7 . To the author's knowledge, there are only a few other full-scale wind pressure measurement studies in transcritical flow, namely (Christensen and Askegaard, 1978;Hansen, 1981;Waldeck, 1989). In fact, all of the above full-scale tests have rough surface on the structure. ...
As the size of modern wind turbines increases, the phenomenon of vortex resonance, which occurs at lower critical speeds due to lower natural frequencies of larger turbines, becomes more significant. Vortex shedding in the wake of a slender structure is still not fully investigated, particularly with regard to the Reynolds number mismatch between small-scale models and the full-scale structure. The vortex shedding load with Re = 4-10x10^6 is addressed in this paper by investigating a full-scale measurement on a large wind turbine tower. The aerodynamic coefficients and vortex shedding load parameters are studied based on the measurement of wind pressure around the circumference of the tower. The results are compared to previous studies and values suggested in related standards. A detailed methodology for data evaluation is presented. As local parameters have been measured, the work marks the distinction between local and global parameters, in particular for the Strouhal number. Although this paper focuses on the tower-only configuration (without nacelle), the measurements are also carried out for a turbine including rotor-nacelle assembly (RNA), which allows the effect of blade position and rotation of the parked wind turbine on the lift coefficient of the tower to be studied.
... [5] and [6] present a comparison between predicted and measured of maximum amplitudes of cross-wind oscillation. Following notable full-scale measurements that include wind pressure measurement such as [1][3][6] [7][8] and [9] conducted the measurement on concrete towers employing rough surfaces. A measurement campaign related to this paper covers the wind pressure and response measurements on very smooth wind turbine towers in both tower-only and with RNA (rotor-nacelle assembly) configurations. ...
From July 2021, a full-scale measurement campaign is carried out on two wind turbine towers with smooth surfaces (k/D ≈ 1.0·10- ⁶ ). Tower response (through accelerations) and wind pressure on the surface are measured. Throughout the one-year monitoring period, there were challenges in transferring full-scale data into a ready-to-use VIV data set. For example, the spatially varying wind conditions despite the small distance between the met masts and the towers. This work aims to provide a ready-to-use full-scale data set for the development of VIV prediction models. A data selection approach based on three simultaneous measurements of wind conditions and maximum moving standard deviation of oscillations s proposed. In addition, the load parameters obtained from the wind pressure measurements in the field and from wind tunnel tests are considered. An enhanced calculation is carried out by defining local aerodynamic damping for sectional heights of the tower. A comparison of the data set with the calculated response is presented to assess the calculation method and to give ideas on sensitive input parameters considering the full-scale condition.
... [5] and [6] present a comparison between predicted and measured of maximum amplitudes of cross-wind oscillation. Following notable full-scale measurements that include wind pressure measurement such as [1][3][6] [7][8] and [9] conducted the measurement on concrete towers employing rough surfaces. A measurement campaign related to this paper covers the wind pressure and response measurements on very smooth wind turbine towers in both tower-only and with RNA (rotor-nacelle assembly) configurations. ...
From July 2021, a full-scale measurement campaign is carried out on two wind turbine towers with smooth surfaces (k/D ~ 1.0∙10-6). Tower response (through accelerations) and wind pressure on the surface are measured. Throughout the one-year monitoring period, there were challenges in transferring full-scale data into a ready-to-use VIV data set. For example, the spatially varying wind conditions despite the small distance between the met masts and the towers. This work aims to provide a ready-to-use full-scale data set for the development of VIV prediction models. A data selection approach based on three simultaneous measurements of wind conditions and maximum moving standard deviation of oscillation is proposed. In addition, the load parameters obtained from the wind pressure measurements in the field and from wind tunnel tests are considered. An enhanced calculation is carried out by defining local aerodynamic damping for sectional heights of the tower. A comparison of the data set with the calculated response is presented to assess the calculation method and to give ideas on sensitive input parameters considering the full-scale condition.
... Waldeck [130] found the super-critical pressure distribution in the rear to be larger than Christensen and Askegaard's when measuring the pressure distribution on a South African chimney using 16 taps at 3 different heights. In a separate study, Waldeck [126] also compared the experimentally obtained lift spectrum to the same theoretical lift spectrum. ...
Vibrations due to the alternating shedding of vortexes (vortex-induced vibrations) are a great concern when designing industrial chimneys. These vibrations are complex and can give large amplitudes of motion at low speeds. There are many methods for predicting these vibrations (e.g. wind tunnels or predictive models) but they need improvements.An experiment in a large wind tunnel revealed important, new knowledge on the vortex-shedding frequency which will help predict vortex-induced vibrations using wind tunnels. Instead of a finding a single vortex-shedding frequency, either in the range 0.25-0.27 or near 0.2 as in previous studies, two distinct Strouhal numbers were found at around 0.2 and 0.25.In addition, the spatial unsteady pressure distributions and forcing results at large-scale helped validate an experimental method for simulating the high Reynolds number flow in smaller wind tunnels. These tests showed that surface roughness can trigger high Reynolds number flow and mostly reproduce the spatial pressure distributions. While promising, the vortex-shedding frequencies and forces were different at small-scale than at large-scale.Turbulent atmospheric boundary layers were found to affect the response more than the surface roughness in 3D aeroelastic tests. When testing a rough and a smooth cylinder with a turbulent boundary layer, the responses were similar but the vibration amplitudes and differences increased when testing without the boundary layer. The importance of the turbulent boundary layer on the response was corroborated in a field experiment on a chimney exposed to naturally varying turbulence profiles.Lastly, ways to improve analytic modeling of predicting vortex-induced vibrations were found by finding the best model for a given situation. This was done using two classical design models and a newly approximated model and the best predictive model was found to depend on the product of mass and damping. When this product was low, the newly approximated model worked best while one of the design models was better when the mass-damping product was high.
... Melbourne et al. (1983) made measurements of the wind-induced responses of and surface pressures around a 265 m high reinforced concrete stack at Re ¼ 2 Â 10 7 . Waldeck (1989) measured mean pressure distribution around a 300 m concrete chimney. A series of field measurements on wind pressures around cooling towers were conducted by Zhao et al. (2017). ...
... Melbourne et al. (1983) made measurements of the wind-induced responses of and surface pressures around a 265 m high reinforced concrete stack at Re = 2×10 7 . Waldeck (1989) measured mean pressure distribution around a 300 m concrete chimney. A series of field measurements on wind pressures around cooling towers were conducted by Zhao et al. (2017). ...
Numerous studies have been carried out to measure wind pressures around circular cylinders since the early 20th century due to its engineering significance. Consequently, a large amount of wind pressure data sets have accumulated, which presents an excellent opportunity for using machine learning (ML) techniques to train models to predict wind pressures around circular cylinders. Wind pressures around smooth circular cylinders are a function of mainly the Reynolds number (Re), turbulence intensity (Ti) of the incident wind, and circumferential angle of the cylinder. Considering these three parameters as the inputs, this study trained two ML models to predict mean and fluctuating pressures respectively. Three machine learning algorithms including decision tree regressor, random forest, and gradient boosting regression trees (GBRT) were tested. The GBRT models exhibited the best performance for predicting both mean and fluctuating pressures, and they are capable of making accurate predictions for Re ranging from 10^4 to 10^6 and Ti ranging from 0% to 15%. It is believed that the GBRT models provide very efficient and economical alternative to traditional wind tunnel tests and computational fluid dynamic simulations for determining wind pressures around smooth circular cylinders within the studied Re and Ti range.
Many high-flexible structures with circular sections (chimneys, etc.) tend to be damaged by vortex-induced vibration (VIV in short). As the direct guidance of wind-resistant design of circular high structures, the wind load code is responsible for wind-induced damage. In view of so many failure cases of circular high structures, it is necessary to study the applicability of current wind load codes. In this paper, the VIV displacements of six chimneys are calculated using European (approach 1, 2), Chinese, Japanese, Canadian, and American wind load codes/recommendations, respectively, and the calculated displacements are compared with the full-scale measured results. The comparison shows that for steel chimneys, the displacements calculated by Japanese recommendation and Chinese code are about only 30% of the full-scale measured value, and those calculated by Canadian code and approach 1 of European code are about 70% of the measured value. For reinforced concrete (RC) chimneys, the calculated displacements of Chinese codes are smaller than the full-scale measured values, while the calculated values of other codes are far greater than the full-scale measured results, with the difference between them even more than ten times. On the whole, there is a significant difference between the results of the VIV displacement calculated by the wind load codes/recommendations and the actual measured value, and the calculated results of current codes/recommendations are differ from one another, thus giving rise to a contradictory phenomenon of “the same structure, but different design wind load” and making the wind-resistant design of circular high structure kind of blind. The purpose of this discussion is to clarify the objective problems of current wind load codes of circular tall structures, which can provide a reference for further research.
This paper presents results of calculations performed according to our own semi-empirical mathematical model of critical vortex excitation. All calculations are carried out using own computer program, which allows the simulation of both the across-wind action caused by vortices and the lateral response of analysed structures. Vortex excitation simulations were performed in real time taking into account wind-structure interaction. Several structures of circular cross-sections were modelled using a FEM program and calculated under the action of critical vortex excitation. Six steel chimneys, six concrete chimneys and two concrete towers were considered. The method of selection and estimation of the experimental parameters describing the model are also presented. Finally, the results concerning maximum lateral top displacements of the structures are compared with available full-scale data for steel and concrete chimneys.
The present study concerns with the spectral description of the atmospheric boundary layers (ABLs) for appropriate modeling for studying the wind effects on structures. By fitting a functional spectral form to the measured wind velocity data obtained in wind tunnel (WT) as well as in nature, it is shown that the Fichtl-McVehil form of spectrum fits better. The estimation of spectral parameters like turbulence intensities, integral length scales and small scales of wind velocity and their influence on the geometric scale (or time scale) are discussed. It is concluded that proper estimation of the spectral parameters of the simulated ABLs and their variation along the height of WT help in comparing the results obtained from different sources (WT tests) for identifying the influences of various flow/body parameters on the wind-induced effects and for formulating improved modeling of wind-structure interactions.
Full-scale measurements of wind pressures around a 200m concrete chimney and associated deflections and oscillations have been performed continuously since 1979. Records of strong typhoon and monsoon winds have been analysed and the characteristics of wind pressures and forces in the supercritical Reynolds number region have been obtained. As a result, alternative vortex shedding has been confirmed and it has been shown that the chimney deflects statically due to mean drag, and oscillates around its mean deflected position. Excellent across-wind oscillation due to fluctuating lift has also been confirmed.
Various comparisons between the observed across-wind response of a 300m concrete chimney and the response predicted by the well known model developed by Vickery and Basu [1983] are presented. It is shown that the model performs remarkably well when the predicted response is based on the observed total damping, which suggests that the aerodynamic damping is positive for the small amplitudes characteristic of concrete chimneys.
The design of natural-draft cooling towers is dominated by wind action. With respect to the response of the structure the wind load may be divided into a static, a quasistatic, and a resonant part. The effect of surface roughness of the shell and of wind profile on the static load is discussed. The quasistatic load may be described by the variance of the pressure fluctuations and their circumferential and meridional correlations. The high-frequency end of the pressure spectra and of the coherence functions are used for the analysis of the resonant response. In general, the resonant response is small even for very high towers. It increases overlinearly with wind velocity. Equivalent static loads may be defined using appropriate gust-response factors. These loads produce an approximation of the behavior of the structure and in general are sufficiently accurate.
This paper describes an instrumentation system developed specifically for the measurement of wind effects on large structures. The design of the system was based entirely on digital techniques to overcome some of the problems associated with full-scale measurements. An inductive phase difference technique was used to extend the digital concept to the pressure transducer level. Two of these systems are currently employed in measurements involving an aircraft hangar and a power station chimney.The advantages and also the disadvantages of the approach approach are discussed.
The development by the National Building Research Institute (NBRI) of a portable pressure source, with applications in both wind-tunnel and in full-scale environments, is described. The instrument, which is equally suited to the static or dynamic calibration of pressure transducers, contains an electronic controller using a pneumatic signal generator as the actuator. Similar signal generators are used in a number of wind-tunnel laboratories for the dynamic calibration of tubing systems containing restrictors and pneumatic averaging devices. The overall operation of the pressure source is controlled by a built-in microprocessor.An approach to overcome the obstacles normally facing the occasional user of microprocessors as instrument controllers is described, and the versatility of the instrument is demonstrated by a number of applications.
Thesis (Phd)--University of Western Ontario, 1982. 7 positive microfiche.
The development of a cable-suspended barometric pressure probe
- J L Naldeck
J.L. Naldeck, The development of a cable-suspended barometric pressure probe, Internal Report 8618, Structural and Geotechnical Engineering Division, National Building Research Institute, Council for Scientific and Industrial Research, Pretoria, June 1986.
Zur stationären Windbelastung rotationssymmetrischer Bauwerke im Bereich transkritischer Reynoldszahlen
- Niemann
Methods for determining the free-stream wind speed from the measured pressure distribution around a chimney
- Waldeck
The development of a cable-suspended barometric pressure probe
- Waldeck
Measurement of the wind loading on Fawley generating station chimney
- Tunstall