The region from the tube inlet to t

The region from the tube inlet to the point at which the boundary layer merges at the centerline is
called the hydrodynamic entry region, and the length of this region is called hydrodynamic entry length. The entry length is much longer in laminar flow than it is in turbulent flow. But at very low Reynolds numbers, Lh is very small (Lh = 1.2D at Re = 20).

Hasil (Bahasa Indonesia) 1:

Daerah dari tube inlet ke titik di mana lapisan batas menyatu di tengah disebut wilayah hidrodinamik entri, dan panjang wilayah ini disebut hidrodinamik catatan panjang. Catatan panjang lebih lama dalam laminar aliran dari dalam turbulent aliran. Tetapi di nomor Reynolds sangat rendah, Lh sangat kecil (Lh = 1.2D di Re = 20).