What does Modi think?

Mody diagram shows the functional relationship between resistance coefficient λ and δ/d and Re.

1, Chamoditu. Firstly, the Reynolds number Re of the flow is determined, and the corresponding abscissa is checked on the Modi diagram;

2. Look up the table "absolute roughness of pipe wall △", divide it by the pipe diameter d, and if it is a non-circular pipe, divide it by the equivalent diameter de, and calculate △/d, which corresponds to the right ordinate of Mody diagram and the curve of Mody diagram area center.

3. According to Reynolds number Re on the abscissa and delta/d on the right ordinate, a point on the central curve of Modi map area is determined correspondingly, which corresponds to the resistance coefficient λ on the left ordinate of Modi map.

4. Then calculate the resistance along the pipeline according to λ.

Moditu is divided into five districts. On the far left is the laminar flow region, where the drag coefficient is directly 64/Re. The second one on the left is the transition zone. Modi is targeting industrial pipelines. This transition zone is difficult to describe, so it is generally extended by turbulence curve.

The third is the turbulent region. It is necessary to combine Re and K/d, first determine Re, that is, the abscissa, and then determine K/d, that is, the ordinate on the right. When determining K/D, it is not the parallel abscissa that intersects with the vertical line of Re just now, but the curve roughly similar to this area intersects with the vertical line of Re, and the abscissa to the right of the intersection point is the resistance coefficient at this time.

The fourth is the square area of resistance, which is only related to K/d. Look at the K/D value directly, and then the corresponding left ordinate is the resistance coefficient value.

Finally, the hydraulic smoothing curve only needs to look at re, and it is a line, not a surface. That's basically it. There are many great gods in Zhihu. Please give me some advice if there is anything wrong.