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Show heat loss between a model and a prototype, it is necessary to increase a wall thickness of the model or to heat the model from outward by an 'electrical heater or a high temperature gas. 3. Analogy of flow pattern Flow pattern in fluid dynamic factor is very important as it relates with three influential factors as is shown in Table 2. The conventional fluid dynamics teaches us that the geometrical configuration of the combustor and Reynolds number does not ·need to be kept constant in order to maintain the same flow pattern against the scale change. However, in the practical scale up, it is sometimes mentioned that Reynolds number should not be always kept constant to realize the same flow pattern when Reynolds number is over 104-105• 7) This means that the similar flow pattern can be obtained regardless of Reynolds number as far as the fully turbulent field is realized. However, an adequacy of this experience has to be examined from the fluid dynamics point. In the fully developed turbulent field, turbulent momentum transfer controls the overall momentum transfer compared to the molecular momentum transfer. Consequently, the average flow pattern is not determined by real Reynolds number but determined by apparent Reynolds number which is Re=VOL/ £ m Here, £m means turbulent eddy viscosity. and L is the representative length. model8), £ m is represented by turbulent 1 as (1) Where, C1 is the proportional constant. kl/2 ex: Uo' lex: ' L. Then, £ m ex: VoL This expression leads to Re=VoL/ £ m=const Vois average velocity According to Kolmogoroff energy k and eddy scale If one can assume that Hence, an apparent Re number can be maintained constant 3 |