Computer rack cooling system with variable airflow impedance

1. A computer system, comprising:

a computer rack configured to support a plurality of computer chassis in a computer stack region of the computer rack;

a cooling plenum configured to draw air from a back side of a computer chassis supported in the computer rack and exhaust the air through an outlet port; and

an airflow control member mounted to the computer rack and positioned between the cooling plenum and the computer stack region and providing an impedance to airflow between the computer stack region and the cooling plenum, the airflow control member providing a greater airflow impedance to a first portion of the computer stack region than to a second portion of the computer stack region;

wherein the airflow control member comprises a plate having a plurality of apertures formed therein, the sizes of the apertures increasing with distance from the outlet port, wherein the rates of the airflow through apertures at each distance from the outlet port are configurable to be similar;

wherein the airflow control member comprises a plurality of adjustable dampers, each of the plurality of apertures being associated with one of the plurality of adjustable dampers;

wherein each of the plurality of adjustable dampers includes a substantially semi-circular shield that is rotatable to full open, to cover a portion of, and to fully close one of the plurality of apertures; and

wherein each of the plurality of adjustable dampers is independently adjustable.

2. The computer system of claim 1 , wherein:

the first portion of the computer stack region is closer to the outlet port than the second portion of the computer stack region.

3. The computer system of claim 1 , further comprising:

a fan provided in the outlet port to draw air from the cooling plenum out of the outlet port.

4. A computer system, comprising:

a computer rack configured to support a plurality of computer chassis in a computer stack region, the computer stack region comprising a first portion configured to support a first computer chassis and a second portion configured to support a second computer chassis, the first portion closer than the second portion to an air outlet port; and

one or more plates mounted to the computer rack and positioned adjacent the computer stack region, the one or more plates comprising a plurality of apertures, the plurality of apertures including a first set of one or more apertures positioned adjacent the first portion of the computer stack region and a second set of one or more apertures positioned adjacent the second portion of the computer stack region, the second set of apertures having a larger total aperture area than the first set of apertures;

wherein air flowing from the computer stack region to the outlet port passes through the plurality of apertures;

wherein the sizes of the apertures increase with distance from the outlet port, wherein the rates of the air flowing through apertures at each distance from the outlet port are configurable to be similar;

wherein the airflow control member comprises a plurality of adjustable dampers, each of the plurality of apertures being associated with one of the plurality of adjustable dampers;

wherein each of the plurality of adjustable dampers includes a substantially semi-circular shield that is rotatable to fully open, to cover a portion of, and to fully close one of the plurality of apertures; and

wherein each of the plurality of adjustable dampers is independently adjustable.

5. The computer system of claim 4 , further comprising a first computer chassis supported in the first position of the computer stack region and a second computer chassis supported in the second portion of the computer stack region.

6. The computer system of claim 4 , further comprising seals adapted to interface the one or more plates with computer chassis in the computer stack region.