Chế độ Siêu_vượt_âm

Hypersonic flow can be approximately separated into a number of regimes. The selection of these regimes is rough, due to the blurring of the boundaries where a particular effect can be found.

Perfect gas

In this regime, the gas can be regarded as an ideal gas. Flow in this regime is still Mach number dependent. Simulations start to depend on the use of a constant-temperature wall, rather than the adiabatic wall typically used at lower speeds. The lower border of this region is around Mach 5, where ramjets become inefficient, and the upper border around Mach 10-12.

Two-temperature ideal gas

This is a subset of the perfect gas regime, where the gas can be considered chemically perfect, but the rotational and vibrational temperatures of the gas must be considered separately, leading to two temperature models. See particularly the modeling of supersonic nozzles, where vibrational freezing becomes important.

Dissociated gas

In this regime, diatomic or polyatomic gases (the gases found in most atmospheres) begin to dissociate as they come into contact with the bow shock generated by the body. Surface catalysis plays a role in the calculation of surface heating, meaning that the type of surface material also has an effect on the flow. The lower border of this regime is where any component of a gas mixture first begins to dissociate in the stagnation point of a flow (which for nitrogen is around 2000 K). At the upper border of this regime, the effects of ionization start to have an effect on the flow.

Khí ga ion-hóa

In this regime the ionized electron population of the stagnated flow becomes significant, and the electrons must be modeled separately. Often the electron temperature is handled separately from the temperature of the remaining gas components. This region occurs for freestream flow velocities around 10–12 km/s. Gases in this region are modeled as non-radiating plasmas.

Chế độ bức xạ cưỡng bức

Ở trên 12 km/s, sự truyền nhiệt cho một phương tiện thay đổi từ bị chi phối sang triệt để. Mô hình khí trong chế độ này được chia thành hai lớp:

  1. Lớp quang mỏng: nơi khí không hấp thụ lại bức xạ phát ra từ các phần khác của khí
  2. Lớp quang dày: nơi bức xạ phải được coi là một nguồn năng lượng riêng biệt.

Việc mô hình hóa các loại khí dày quang học là vô cùng khó khăn, do tính toán bức xạ tại mỗi điểm, tải trọng tính toán theo lý thuyết sẽ tăng theo cấp số nhân khi số lượng điểm được xem xét tăng lên.