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Article

Mete Koken, Ismail Aydin and Akis Sahin

High head gates are commonly used in hydropower plants for flow regulation and emergence closure. Hydrodynamic downpull can be a critical parameter in design of the…

Abstract

Purpose

High head gates are commonly used in hydropower plants for flow regulation and emergence closure. Hydrodynamic downpull can be a critical parameter in design of the lifting mechanism. The purpose of this paper is to show that a simplified two-dimensional (2D) computational fluid dynamics solution can be used in the prediction of the downpull force on the gate lip by comparison of computed results to experimentally measured data.

Design/methodology/approach

In this study, ANSYS FLUENT CFD software was used to obtain 2D numerical solution for the flow field around a generic gate model located in a power intake structure which was previously used in an experimental study. Description of the flow domain, computational grid resolution, requirements on setting appropriate boundary conditions and methodology in describing downpull coefficient are discussed. Total number of 245 simulations for variable gate lip geometry and gate openings were run. The downpull coefficient evaluated from the computed pressure field as function of gate opening and lip angle are compared with the experimental results.

Findings

The computed downpull coefficient agrees well with the previous experimental results, except one gate with small lip angle where a separation bubble forms along the lip, which is responsible from this deviation. It is observed that three-dimensional (3D) effects are confined to the large gate openings where downpull is minimum or even reversed.

Research limitations/implications

In large gate openings, three dimensionality of the flow around gate slots plays an important role and departure from 2D solutions become more pronounced. In that case, one might need to perform a 3D solution instead.

Practical implications

This paper presents a very fast and accurate way to predict downpull force on high head gates in the absence of experimental data.

Originality/value

An extensive amount of simulations are run within the scope of this study. It is shown that knowing its limitations, 2D numerical models can be used to calculate downpull for a wide range of gate openings without the need of expensive experimental models.

Details

Engineering Computations, vol. 34 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

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Book part

Nurhayat Iflazoglu and Ipek Itir Can

While the number of tourists worldwide is expected to reach 1.8 billion people by 2030, tourism destinations try to meet demand for increasing tourism. However, some…

Abstract

While the number of tourists worldwide is expected to reach 1.8 billion people by 2030, tourism destinations try to meet demand for increasing tourism. However, some tourism destinations are experiencing a maturity period of destination life cycle intensively. During these mature periods, while they meet the demand above their tourism carrying capacity, they encounter some problematic issues. In tourist destinations such as Venice, Barcelona and Paris, the negative feelings developed by the local people towards overtourism or tourists result in serious problems like negative destination images, tourism phobia, etc. In these destinations, to prevent the negative consequences of overtourism, destination stakeholders should develop solutions to these problems. There are many solution techniques for the problems which cause overtourism. One of them is the different tourism types which have been developed as an alternative to mass tourism. These alternative tourism types can be handled as a method for solving problems revealed through excess demand in tourism destinations at risk. For example, some tourism destinations which have both beach tourism and nature-based tourism types can bring nature-based tourism activities to the forefront with promotion and marketing activities and therefore, the tourism demand could be balanced between these tourism types. In this context, firstly, comprehensive literature review of overtourism and alternative tourism will be conducted in this study. And then the different types of tourism such as ecotourism, cultural tourism and responsible tourism will be discussed in detail and their relation in reducing the negative consequences of overtourism will be investigated theoretically via secondary data. Therefore, alternative tourism potentials will be investigated and tried to present the managerial suggestions for the development of different alternative types of tourism. As a result, it has been seen that, alternative tourism not only contributes to the growth of tourism in both popular and remote destinations but also makes sure that destinations get their fair share in income distribution of the country.

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Article

Levent Sumer and Beliz Ozorhon

Under the current Coronavirus Disease 2019 (COVID-19) pandemic circumstances where the gold prices are increasing and the stocks are in free fall, this research aims to…

Abstract

Purpose

Under the current Coronavirus Disease 2019 (COVID-19) pandemic circumstances where the gold prices are increasing and the stocks are in free fall, this research aims to compare the returns of gold prices and Turkish real estate investment trust (T-REIT) index by covering the 2008 global financial crisis, 2018 Turkish currency crisis and 2020 COVID-19 pandemic-based economic crisis periods and examine the effects of the returns of gold and the T-REIT index on each other, a research area that has been limited in the literature.

Design/methodology/approach

For the empirical analysis, vector auto regression model was used, and Augmented Dickey–Fuller and Granger causality tests were also conducted. The average returns were compared with the coefficient of variation analysis.

Findings

The results of the study exhibited that except for the 2008 global financial crisis period, 2018 Turkish currency crisis and 2020 COVID-19 pandemic-based economic crisis, the T-REIT index performs better than gold prices, but it is a riskier instrument, and both investment instruments do not affect the returns of each other. The segmentation of both instruments recommends the fund managers including both tools for diversification of a portfolio.

Research limitations/implications

In Turkey, gold prices are valued based on the fluctuations of the global gold prices, as well as the Turkish Lira/US Dollar currency exchange rates. The effect of the exchange rates may be considered in future studies, and the study may be conducted based on the USD values of the T-REIT index and global gold prices. Further studies may also include the comparison between the T-REIT index returns and a set of commodities such as the Goldman Sachs Commodity Index. This study covered only the first five months of 2020 to analyze the COVID-19 pandemic-based economic crisis initial effects, and a successor study is also recommended by including more new data of the post-COVID-19 pandemic and comparing both results.

Practical implications

The results of the research are expected to contribute to the REIT literature and give insight to investors about their investment choices while including both investment tools in their portfolio, especially for the future conditions of the new COVID-19 pandemic-based economic crisis.

Social implications

The study may provide insight for individuals, especially those who are considering possible investment options in the Turkish real estate market in the post-COVID-19 pandemic crisis.

Originality/value

Gold and real estate have always been considered as important investment instruments. Gold is commonly accepted as a safe haven in the literature, and the REITs are considered as long-term investment instruments by many scholars. While gold prices increase in the windy periods, the returns of real estate investments have more cyclical movements based on mostly the macroeconomic conditions and its integration with stock markets, yet the real estate is a common long-term investment tool, especially because of the regular income it generates for the retirement years. By covering three crisis periods including the COVID-19 pandemic-based economic crisis effects, making research about two important investment tools would contribute to the literature, especially in which the studies in this area were very limited.

Details

Journal of European Real Estate Research , vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1753-9269

Keywords

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