Investigation a single-spiral vortex in a swirl flow

The work is aimed at a detailed study of large-scale helical vortex structures emerging in a high turbulent intensively swirling flow. It was shown that the vortex formed in the chamber by installing diaphragm with shifted outlet is folded into a single-helical vortex. The flow visualization shows that although the vortex axis performs slow oscillations (precession), on average this structure is fixed in space. The velocity fields were measured with the aid of a nonintrusive method of flow diagnostics (PIV). Verification of the calculation results obtained using a LES simulation was performed based on measured experimental data to confirm the correctness of the chosen mathematical modelling approach. It has been asserted that the investigated regimes are in a self-similarity area relative to Reynolds number

LDA analysis of swirling flow in a hydro turbine draft tube

The work reports on experimental study of flow and pressure pulsations in draft-tube of a laboratory air model of a Francis hydro-turbine operating over a broad range of regimes corresponding to different combinations of the runner rotation speed and flowrates. The velocity measurements using a computer-automated laser-Doppler anemometer and the pressure recording by wall-mounted acoustic sensors for a selection of operating conditions reveal different patterns of the swirling flow, with clearly identifiable regimes with the maximum flow pulsations at non-optimal operating conditions. The regimes with distinct precessing vortex cores show notable rearrangement of the velocity fields, accompanied by an increase in the amplitude of the pressure pulsations, as confirmed by the peaks of the spectra of pressure signals from wall-mounted microphones

An Experimental and a Numerical Study of Precessing Vortex Core in the High Swirl Number Flow Conditions

Статья посвящена численному и экспериментальному исследованию нестационарных режимов закрученного течения в модельной вихревой камере с формированием прецессирующего вихревого ядра. Эксперименты по исследованию пульсационных характеристик течения проводили с помощью гидроакустических датчиков, скоростной визуализации и бесконтактной PIV-системы. Численные расчеты вели с использованием гибридной модели турбулентности DES, реализованной в коммерческом CFD-пакете Star-CCM+.The paper is devoted to a numerical and an experimental study of non-stationary modes of the swirled flow in the modeling vortex chamber with precessing vortex core (PVC) formation. The experimental research of flow pulsationcharacteristics were spent with use of hydroacoustic sensors, high-speed visualization and contactless PIV systems. Numerical simulations were spent with use of hybrid turbulentDES (Detached Eddy Simulation) model realized in the commercial CFD packet Star-CCM+

LDA analysis of swirling flow in a hydro turbine draft tube

The work reports on experimental study of flow and pressure pulsations in draft-tube of a laboratory air model of a Francis hydro-turbine operating over a broad range of regimes corresponding to different combinations of the runner rotation speed and flowrates. The velocity measurements using a computer-automated laser-Doppler anemometer and the pressure recording by wall-mounted acoustic sensors for a selection of operating conditions reveal different patterns of the swirling flow, with clearly identifiable regimes with the maximum flow pulsations at non-optimal operating conditions. The regimes with distinct precessing vortex cores show notable rearrangement of the velocity fields, accompanied by an increase in the amplitude of the pressure pulsations, as confirmed by the peaks of the spectra of pressure signals from wall-mounted microphones.ChemE/Transport Phenomen

Исследование влияния подачи воздуха на вихревую структуру течения в тангенциальной камере

In the work, numerical simulations of a turbulent swirling flow in a model tangential chamber were performed. Depending on the swirl number and water flow discharge, various flow regimes are observed: a column vortex, a spiral vortex, a double spiral vortex. In this paper, a study was made of admission air to control the transition between flow regimes. It is shown that when a gas phase is added, a transition from a two-helix structure to a single helical vortex occurs. This phenomenon reproduces the effect observed in the experimentВ работе выполнено численное моделирование турбулентного вихревого течения в модельной тангенциальной камере. В зависимости от закрутки потока и расхода воды в камере наблюдаются различные режимы течения: колонообразный вихрь, спиральный вихрь, двойной спиральный вихрь. В работе проведено исследование влияния добавления воздуха на переход между режимами течения. Показано, что при добавлении второй фазы происходит переход от двухспиральной структуры к одиночному спиральному вихрю. Данное явление воспроизводит эффект, наблюдаемый в эксперимент

Numerical and Experimental Simulation fo the Flow in the Water Turbine Draft Tube

В работе проведено экспериментальное и численное изучение структуры закрученного турбулентного потока в модельной отсасывающей трубе гидротурбины. Получено хорошее согласование расчетных и экспериментальных данных. Обнаружена сильная неравномерность потока за поворотным коленом, существенно снижающая пропускную способность отсасывающей трубы.We performed experimental and numerical study of the structure of swirling turbulent flow in the model draft tube turbine. Obtained a good agreement between calculated and experimental data. A strong non-uniformity of flow at a turning knee, severely reduces the capacity of the draft tu