Definiens:

A system or object whose structure is a temporary state created by flowing streams of energy, material or information.

Examples of flow systems.
Simple ones: a flame, a vortex
More complicated: a bank account, a company
and the most complex one: a living object

For this type of system the usual name is an open system. However, since there are many definitions of open systems, the physics of life recommends the use of a more precise and informative definiendum: flow system.

More:

One of the simplest models of a flow system is a bathtub and filling it with water from the pipe (the water service pipe belongs to the environment). The water flows through the system all the time and at any given moment, a proportion of the water is part of the system. From the point of view of the system, we can say that the water, as a resource, is continuously (or occasionally) flowing through the system, temporarily becoming its part. Properties examined by an observer may be, for example: the total weight of the system or the water level.

Both the properties and their states depend on the amount of water entering the bathtub and the diameter of the plughole. With our own bathing experience, we know that it is difficult to open the tap, without the plug, in such a way that the water level will remain constant. Usually the level will either increase or decrease. To maintain the desired level, one must periodically loosen or tighten the tap or block the outlet with your heel. The bather, therefore, performs the role of a regulator of a system property, which is, in this case, the water level. A similar system is a lavatory cistern in which the role of the regulator is performed by the ballcock which cuts off the water supply when the water level reaches a certain point.

Another example of the flow system is our bank account. The property that interests us the most is, of course, its status, i.e. how much money we have at the moment. And this results from the difference between two flows: incomings and outgoings. Both of these consist of sub flows, for example: contributions from the employer in respect of salary, payments from other sources, ATM withdrawals and transfers from which we pay our bills.

The most mysterious flow systems are living objects, including, of course, ourselves. All the properties of living objects and the conditions of these properties is a temporary state of various flows. From the perspective of systems theory, putting a jacket on is comparable to putting the plug in a bath. In the first case, we reduce the amount of outgoing heat (flow of energy), whilst in the other, we reduce the amount of water leaving the bath (flow of matter). We all eat - we absorb matter and energy to eventually expel them in processed form. We also get information from our environment, without which we would not be able to function. In turn we pass our information to the surrounding environment by our mimics, smell and speech, for example.

To sum up: generally, flow systems and the state of their properties result from different types of interactions between flows of matter, energy and information.

Remarks:

• The main problem in the analysis of flow systems is the difficulty in its visualization, for example, the inability to draw a schematic. Let us analyse such a system: In the new operation against the Soviet Western Front, plans involved the Army Group "Center" and part of the 16th Army. In the first wave [This requires already several drawings to show the successive waves] 16 divisions, comprising of nine armored divisions, six motorized divisions and one motorized brigade, would have to attack. Second-line troops, after dismantling the encircled enemy troops to the west of Minsk, would have to cross the rivers Dvina and the Dnieper. Armored Group Hoth and Guderian would not have to wait [In a diagram it is difficult to show the change of the flow as it depends upon the decisions that would have been made] for their approach, but attack towards Smolensk, cut the troops of the Soviet Western Front into pieces and surround them.

  Even this translation into English was quite difficult!

• All living objects (cells, a complex group of cells, organs, human beings, societies) can be regarded as a flow system.

  

• Factories and entreprises can also be regarded as flow systems.