Vladimir Lukyanov's 1936 Water Integrator solved differential equations with interconnected water-filled pipes

The Soviet engineer Vladimir Sergeevich Lukyanov built a Water Integrator in 1936 — a room-sized hydraulic analog computer in which water levels in interconnected chambers stood for the values of variables, and the flow of water between chambers physically integrated the governing equations. Unlike the later British MONIAC, which modeled money flows, Lukyanov's machine was a general differential-equation solver: he built it to compute the temperature and cracking behaviour of setting concrete in large structures, a partial differential equation problem that had no practical numerical method at the time.

On the reported account, the integrators were later applied to a wide range of civil and industrial engineering problems — canals, railways, mines, and rocket production — were exported to China, Poland, Bulgaria, and Czechoslovakia, and remained in official use into the 1980s. All of these specifics are [unverified-source]: they rest on a single Tier-4 Wikipedia article, and for an obscure, load-bearing historical entity that clears the "uncontested Tier 3–4" bar only weakly. See question-verify-lukyanov-water-integrator-primary.

Built thirteen years before the MONIAC, in the opposite Cold War bloc and for an unrelated domain, the Water Integrator is the earlier half of a convergent-invention pair — claim-hydraulic-analog-computers-independently-invented-economics-engineering — which sits with the vault's other independent-discovery threads (claim-reverse-mode-multiple-independent-discovery, claim-labview-max-independent-patch-cord-convergence) and against Chandler's skeptical reading of such convergences.